Please help with a simple GUI.

[jay smith]

Hello,

I am having some problems with a simple GUI program that I am writing for school. I have read the text and examples a few times, but I can't seem to figure out what I am doing wrong.

If someone can take a look at this and give me some feedback, I would appreciate it.

Thanks,
J

 
 
public class Rational
{
 
private int numer;
private int denom;


Rational()// take no arguments
{
setNumer( 0 );// set numerator to 0
setDenom( 1 );// set denominator to 1

} // end constructor method that takes no arguments

Rational( int numerValue )// take one int argument
{
setNumer( numerValue );// set numerator to the numerValue
setDenom( 1 );// set denominator to 1

} // end constructor method that takes one int argument


Rational( int numerValue, int denomValue )// take two int arguments
{
setNumer( numerValue );// set numerator to the numerValue
setDenom( denomValue );// set denominator to the denomValue

} // end constructor method that takes two int arguments

Rational( String theString )// take one string argument
{
if ( theString.matches( "\\d+[/]\\d+" ) )// if theString matches (digit(all occurences preceding the +)/digit(all occurences preceding the +))
{
String[] results = theString.split( "/" );// split theString into two substrings and store into String array results

setNumer( Integer.parseInt( results[ 0 ] ) );// convert numerator to int and set numerator as the first index of results array 
setDenom( Integer.parseInt( results[ 1 ] ) );// convert denominator to int and set denominator as the second index of results array

} // end if theString is a fraction 

else if( theString.matches( "\\d+" ) )// else if theString matches (digit(all occurences preceding the +)
{
setNumer( Integer.parseInt( theString ) );// convert numerator to int and set numerator to theString
setDenom( 1 );// set denominator to 1

} // end else if the string is not a fraction

} // end constructor method that takes one string argument


public void setNumer( int numerValue )// take one int argument
{
numer = numerValue;// set numerator to numerValue

} // end method setNumer


public void setDenom( int denomValue )// take one int argument
{
denom = denomValue;// set denominator to the denomValue

} // end method setDenom


public int getNumer()// return numerator
{
return numer;// return numerator

} // end method getNumer


public int getDenom()// return denominator
{
return denom;// return denominator

} // end method getDenom


public Rational addRats( Rational ratValue )// take one Rational argument and return a Rational object
{
Rational sum = new Rational();// initialize a new Rational object called sum

// set numerator for the new Rational object by cross multiplying and adding
// ( numer1 * denom2 ) + ( denom1 * numer2 )
sum.setNumer( ( getNumer() * ratValue.getDenom() ) + ( getDenom() * ratValue.getNumer() ) );

// set denominator for the new Rational object
// ( denom1 * denom2 )
sum.setDenom( getDenom() * ratValue.getDenom() );

return sum.reduce();// return reduced fraction

} // end method addRats


public Rational subtractRats( Rational ratValue )// take one Rational argument and return a Rational object
{
Rational difference = new Rational();// initialize a new Rational object called difference

// set numerator for the new Rational object by cross multiplying and subtracting 
// ( numer1 * denom2 ) - ( denom1 * numer2 )
difference.setNumer( ( getNumer() * ratValue.getDenom() ) - ( getDenom() * ratValue.getNumer() ) );

// set denominator for the new Rational object by multiplying denominators
// ( denom1 * denom2 )
difference.setDenom( getDenom() * ratValue.getDenom() );

return difference.reduce();// return reduced fraction

} // end method subtractRats


public Rational multiplyRats( Rational ratValue )// take one Rational argument and return a Rational object
{
Rational product = new Rational();// initialize a new Rational object called product

// set numerator for the new Rational object by straight multiplying
// ( numer1 * numer2 )
product.setNumer( getNumer() * ratValue.getNumer() );

// set denominator for the new Rational object by straight multiplying
// ( denom1 * denom2 )
product.setDenom( getDenom() * ratValue.getDenom() );

return product.reduce();// return reduced fraction

} // end method multiplyRats


public Rational divideRats( Rational ratValue )// take one Rational argument and return a Rational object
{
Rational quotient = new Rational();// initialize a new Rational object called quotient

// set numerator for the new Rational object by straight multiplying with the reciprocal of the second Rational
// ( numer1 * denom2 )
quotient.setNumer( getNumer() * ratValue.getDenom() );

// set denominator for the new Rational object by straight multiplying with the reciprocal of the second Rational
// ( denom1 * numer2 )
quotient.setDenom( getDenom() * ratValue.getNumer() );

return quotient.reduce();// return reduced fraction

} // end method divideRats


public Rational getReduced()// return a Rational object
{
return reduce();// invokes method reduce
//return this;// return reduced fraction

} // end method getReduced


public String toString()
{
if( getDenom() == 1 )// if denominator is 1
{
return getNumer() + "";// return numerator

}

else
{
return getNumer() + "/" + getDenom();// return as a fraction ( numerator/denominator )

}

} // end method toString

 
public double toDouble()
{
double numerDouble = getNumer();// assign numerator to numerDouble
double denomDouble = getDenom();// assign denominator to denomDouble
double ratDouble = ( numerDouble / denomDouble );// assign numerDouble/denomDouble to ratDouble

return ratDouble;// return ratDouble

} // end method toDouble


public boolean denomIsNotZero()
{
if( getDenom() != 0 )// if denom is not 0
{
return true;// return true

} // end if denom is not 0

else
{
return false;// return false

} // end else

} // end method denomIsNotZero

private Rational reduce()
{
int gcd = getGCD( getNumer(), getDenom() );// get greatest common divisor and assign it to gcd

// set denominator to (denominator/gcd) and set numerator to (numerator/gcd)
setDenom( getDenom() / gcd );// reduce denominator by dividing it by the gcd
setNumer( getNumer() / gcd ); // reduce numerator by dividing it by the gcd

return this;// return reduced Rational

} // end method reduce


public int getGCD(int numerValue, int denomValue)
{ 
if ( ( numerValue % denomValue ) == 0 ) // if there is no remainder return denomValue
{
return denomValue;

}// end if there is no remainder  
else
{ 
return getGCD( denomValue, ( numerValue % denomValue ) );

}// end else get gcd of denomValue and the remainder of ( numerValue / denomValue )
 

} // end method getGCD

}

 
//----------------------------------------------
//----------------------------------------------
 
 
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.DecimalFormat;
 
 
public class RationalTester extends JFrame implements ActionListener
{
private Rational rat1;
private Rational rat2;
private Rational ratsResult;
private String output = "";
private String buttonPushed = "";

private JButton addButton, subtractButton, multiplyButton, divideButton;

private JPanel topPanel, middlePanel, bottomPanel;

private JLabel firstRatLabel, blank1Label, secondRatLabel, blank2Label, firstNumerLabel, firstDenomLabel, 
secondNumerLabel, secondDenomLabel, resultLabel;

private JTextField firstNumerField, firstDenomField, secondNumerField, secondDenomField, resultField;
 
private JTextArea displayArea;
 
private Container container;


public RationalTester()
{
super( "Rational Tester" );

container = getContentPane();
container.setBackground( Color.GREEN );

displayArea = new JTextArea();

// create panels
topPanel = new JPanel();
topPanel.setLayout( new GridLayout( 3, 4, 5, 5 ) );

middlePanel = new JPanel();
middlePanel.setLayout( new GridLayout( 3, 4, 5, 5 ) );

bottomPanel = new JPanel();
bottomPanel.setLayout( new GridLayout( 2, 1, 5, 5 ) );

// create components for top panel and add them to top panel
firstRatLabel = new JLabel( "First Rational" );
blank1Label = new JLabel( "          " );
secondRatLabel = new JLabel( "Second Rational" );
blank2Label = new JLabel( "          " ); 

firstNumerLabel = new JLabel( "Numerator" );
firstNumerField = new JTextField( 5 );

firstDenomLabel = new JLabel( "Denominator" );
firstDenomField = new JTextField( 5 );

secondNumerLabel = new JLabel( "Numerator" );
secondNumerField = new JTextField( 5 );

secondDenomLabel = new JLabel( "Denominator" );
secondDenomField = new JTextField( 5 );

topPanel.add( firstRatLabel );
topPanel.add( blank1Label );
topPanel.add( secondRatLabel );
topPanel.add( blank2Label );

topPanel.add( firstNumerLabel );
topPanel.add( firstNumerField );
topPanel.add( secondNumerLabel );
topPanel.add( secondNumerField );

topPanel.add( firstDenomLabel );
topPanel.add( firstDenomField );
topPanel.add( secondDenomLabel );
topPanel.add( secondDenomField );

topPanel.setSize( 250, 250 );

// create components for middle panel and add them to middle panel
addButton = new JButton( "Add Rationals" );
addButton.addActionListener( this );

subtractButton = new JButton( "Subtract Rationals" );
subtractButton.addActionListener( this );

multiplyButton = new JButton( "Multiply Rationals" );
multiplyButton.addActionListener( this );

divideButton = new JButton( "Divide Rationals" );
divideButton.addActionListener( this );

middlePanel.add( addButton );
middlePanel.add( subtractButton );
middlePanel.add( multiplyButton );
middlePanel.add( divideButton );

// create component for bottom panel and add them to bottom panel
resultLabel = new JLabel ( "Results" );
resultField = new JTextField( 7 );

bottomPanel.add( resultLabel );
bottomPanel.add( resultField );

Container myContainer = getContentPane();
myContainer.setLayout( new BorderLayout() );
myContainer.add( topPanel, BorderLayout.NORTH );
myContainer.add( middlePanel, BorderLayout.CENTER );
myContainer.add( bottomPanel, BorderLayout.SOUTH );

setSize( 450, 550 );
setVisible( true );

rat1 = new Rational();
rat2 = new Rational();
}

public void actionPerformed( ActionEvent event )
{
rat1.setNumer( Integer.parseInt( firstNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( firstDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

displayResult( "" );

if( rat1.denomIsNotZero() && rat2.denomIsNotZero() )
{
//buttonPushed = event.getActionCommand();
if( event.getSource() == addButton )
{
//display.setText( rat1.addRats( rat2 ).toString() );
reset();

}

else if( event.getSource() == subtractButton )
{
displayArea.setText( rat1.subtractRats( rat2 ).toString() );
reset();

}

else if( event.getSource() == multiplyButton )
{
displayArea.setText( rat1.multiplyRats( rat2 ).toString() );
reset();

}

else if( event.getSource() == divideButton )
{
displayArea.setText( rat1.divideRats( rat2 ).toString() );
reset();

}
}

}


private void reset()
{
rat1 = new Rational();
rat2 = new Rational();
output = "";
//buttonPushed = "";

}


private void displayResult( String operation )
{
output += rat1.toString() + rat1.toDouble();

displayArea.setText( output );
}


public static void main( String args[] )
{
RationalTester rt = new RationalTester();

rt.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );

}

}
 
 


 

[ July 20, 2005: Message edited by: jay smith ]

[Paul Sturrock]

I am having some problems with a simple GUI program

Could you describe these problems? Or perhaps post a stack trace if your code is throwing an Exception?

[jay smith]

I'm not able to output the results. I am not sure if I am not using toString correctly or what.

Thanks,
J

java.lang.ClassCastException: RationalTester
at sun.applet.AppletPanel.createApplet(AppletPanel.java:712)
at sun.applet.AppletPanel.runLoader(AppletPanel.java:641)
at sun.applet.AppletPanel.run(AppletPanel.java:320)
at java.lang.Thread.run(Thread.java:595)
 

[jay smith]

Does anyone have any suggestions? I have just about reached the point of pulling hair out.

Is it a problem with parseInt?

I am tracing back over it again. If anyone can give me a pointer, I would appreciate it.

Thanks,
J

[jay smith]

OK, I am not getting output because the input values are not getting set.

What am I doing wrong?

I am getting the following errors.

Thanks,
J

  
java.lang.ClassCastException: RationalTester
at sun.applet.AppletPanel.createApplet(AppletPanel.java:712)
at sun.applet.AppletPanel.runLoader(AppletPanel.java:641)
at sun.applet.AppletPanel.run(AppletPanel.java:320)
at java.lang.Thread.run(Thread.java:595)
Exception in thread "AWT-EventQueue-1" java.lang.ArithmeticException: / by zero
at Rational.getGCD(Rational.java:218)
at Rational.reduce(Rational.java:205)
at Rational.divideRats(Rational.java:146)
at RationalTester.actionPerformed(RationalTester.java:180)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1849)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2169)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:234)
at java.awt.Component.processMouseEvent(Component.java:5488)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3093)
at java.awt.Component.processEvent(Component.java:5253)
at java.awt.Container.processEvent(Container.java:1966)
at java.awt.Component.dispatchEventImpl(Component.java:3955)
at java.awt.Container.dispatchEventImpl(Container.java:2024)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4212)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3892)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3822)
at java.awt.Container.dispatchEventImpl(Container.java:2010)
at java.awt.Window.dispatchEventImpl(Window.java:1774)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)
Exception in thread "AWT-EventQueue-1" java.lang.ArithmeticException: / by zero
at Rational.getGCD(Rational.java:218)
at Rational.reduce(Rational.java:205)
at Rational.divideRats(Rational.java:146)
at RationalTester.actionPerformed(RationalTester.java:180)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1849)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2169)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:234)
at java.awt.Component.processMouseEvent(Component.java:5488)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3093)
at java.awt.Component.processEvent(Component.java:5253)
at java.awt.Container.processEvent(Container.java:1966)
at java.awt.Component.dispatchEventImpl(Component.java:3955)
at java.awt.Container.dispatchEventImpl(Container.java:2024)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4212)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3892)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3822)
at java.awt.Container.dispatchEventImpl(Container.java:2010)
at java.awt.Window.dispatchEventImpl(Window.java:1774)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException: component argument pData
at sun.awt.windows.Win32SurfaceData.initOps(Native Method)
at sun.awt.windows.Win32SurfaceData.<init>(Win32SurfaceData.java:448)
at sun.awt.windows.Win32SurfaceData.createData(Win32SurfaceData.java:316)
at sun.awt.Win32GraphicsConfig.createSurfaceData(Win32GraphicsConfig.java:357)
at sun.awt.windows.WComponentPeer.replaceSurfaceData(WComponentPeer.java:332)
at sun.awt.windows.WComponentPeer.replaceSurfaceData(WComponentPeer.java:313)
at sun.awt.windows.WComponentPeer$2.run(WComponentPeer.java:353)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:461)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)
 

[Ernest Friedman-Hill]

From the stack trace, it looks like you're trying to run your program with the appletviewer. But it's not an applet, so that's one part of the problem right there. You need to run your program from the command line using

java RationalTester

The only reason you're getting a GUI on screen is because you're setting everything up in the constructor, which would be a no-no for an applet, anyway.

Another problem is that you carefully display the output in the TextArea "displayArea", which isn't displayed on the screen. You've got "resultsField" on the bottom, there, but it isn't used to display anything!

Otherwise, I'm stumped. Sure looks like it should work, and I can't see what could cause those stack traces. Are you sure you're showing us exactly the same code you're running?

[jay smith]

I have made a few changes to the RationalTester class, but I have not made any changes to the Rational class. The code is posted below. I really appreciate your assistance. I am getting this stack trace:

Exception in thread "AWT-EventQueue-0" java.lang.ArithmeticException: / by zero
at Rational.getGCD(Rational.java:218)
at Rational.reduce(Rational.java:205)
at Rational.divideRats(Rational.java:146)
at RationalTester.actionPerformed(RationalTester.java:178)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1849)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2169)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:234)
at java.awt.Component.processMouseEvent(Component.java:5488)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3093)
at java.awt.Component.processEvent(Component.java:5253)
at java.awt.Container.processEvent(Container.java:1966)
at java.awt.Component.dispatchEventImpl(Component.java:3955)
at java.awt.Container.dispatchEventImpl(Container.java:2024)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4212)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3892)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3822)
at java.awt.Container.dispatchEventImpl(Container.java:2010)
at java.awt.Window.dispatchEventImpl(Window.java:1774)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)
 

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.DecimalFormat;
 

public class RationalTester extends JFrame implements ActionListener
{
private Rational rat1;
private Rational rat2;
private Rational ratsResult;
private String output = "";
//private String buttonPushed = "";

private JButton addButton, subtractButton, multiplyButton, divideButton;

private JPanel topPanel, middlePanel, bottomPanel;

private JLabel firstRatLabel, blank1Label, secondRatLabel, blank2Label, firstNumerLabel, firstDenomLabel, 
secondNumerLabel, secondDenomLabel, resultLabel;

private JTextField firstNumerField, firstDenomField, secondNumerField, secondDenomField, resultField;
 
private JTextArea outputArea;
 
private Container container;


public RationalTester()
{
super( "Rational Tester" );

container = getContentPane();
container.setBackground( Color.GREEN );

outputArea = new JTextArea();

// create panels
topPanel = new JPanel();
topPanel.setLayout( new GridLayout( 3, 4, 5, 5 ) );

middlePanel = new JPanel();
middlePanel.setLayout( new GridLayout( 3, 4, 5, 5 ) );

//bottomPanel = new JPanel();
//bottomPanel.setLayout( new GridLayout( 2, 1, 5, 5 ) );

// create components for top panel and add them to top panel
firstRatLabel = new JLabel( "First Rational" );
blank1Label = new JLabel( "          " );
secondRatLabel = new JLabel( "Second Rational" );
blank2Label = new JLabel( "          " ); 

firstNumerLabel = new JLabel( "Numerator" );
firstNumerField = new JTextField( 5 );

firstDenomLabel = new JLabel( "Denominator" );
firstDenomField = new JTextField( 5 );

secondNumerLabel = new JLabel( "Numerator" );
secondNumerField = new JTextField( 5 );

secondDenomLabel = new JLabel( "Denominator" );
secondDenomField = new JTextField( 5 );

topPanel.add( firstRatLabel );
topPanel.add( blank1Label );
topPanel.add( secondRatLabel );
topPanel.add( blank2Label );

topPanel.add( firstNumerLabel );
topPanel.add( firstNumerField );
topPanel.add( secondNumerLabel );
topPanel.add( secondNumerField );

topPanel.add( firstDenomLabel );
topPanel.add( firstDenomField );
topPanel.add( secondDenomLabel );
topPanel.add( secondDenomField );



// create components for middle panel and add them to middle panel
addButton = new JButton( "Add Rationals" );
addButton.addActionListener( this );
addButton.setBackground( Color.ORANGE );

subtractButton = new JButton( "Subtract Rationals" );
subtractButton.addActionListener( this );
subtractButton.setBackground( Color.ORANGE );

multiplyButton = new JButton( "Multiply Rationals" );
multiplyButton.addActionListener( this );
multiplyButton.setBackground( Color.ORANGE );

divideButton = new JButton( "Divide Rationals" );
divideButton.addActionListener( this );
divideButton.setBackground( Color.ORANGE );

middlePanel.add( addButton );
middlePanel.add( subtractButton );
middlePanel.add( multiplyButton );
middlePanel.add( divideButton );



// create component for bottom panel and add them to bottom panel
resultLabel = new JLabel ( "Results" );
resultField = new JTextField( 7 );

middlePanel.add( resultLabel );
middlePanel.add( resultField );



Container myContainer = getContentPane();
myContainer.setLayout( new BorderLayout() );
myContainer.add( topPanel, BorderLayout.NORTH );
myContainer.add( middlePanel, BorderLayout.CENTER );
//myContainer.add( bottomPanel, BorderLayout.SOUTH );

setSize( 450, 550 );
setVisible( true );

rat1 = new Rational();
rat2 = new Rational();

displayResult( "" );

}




public void actionPerformed( ActionEvent event )
{

if( event.getSource() == firstNumerField || event.getSource() == firstDenomField ||
event.getSource() == secondNumerField || event.getSource() == secondDenomField )
{

rat1.setNumer( Integer.parseInt( firstNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( firstDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

displayResult( "" );

}

else if( event.getSource() == addButton )
{
ratsResult = rat1.addRats( rat2 );
displayResult( "Sum" );

}


else if( event.getSource() == subtractButton )
{
ratsResult = rat1.subtractRats( rat2 );
displayResult( "Difference" );

}

else if( event.getSource() == multiplyButton )
{
ratsResult = rat1.multiplyRats( rat2 );
displayResult( "Product" );

}

else if( event.getSource() == divideButton )
{
ratsResult = rat1.divideRats( rat2 );////////////////////////////////////
displayResult( "Quotient" );

}

}




private void reset()
{
rat1 = new Rational();
rat2 = new Rational();
output = "";

}




private void displayResult( String operation )
{
output += "First Rational " + rat1.toString() + " (" + rat1.toDouble() + ")\n";

output += "Second Rational " + rat2.toString() + " (" + rat1.toDouble() + ")\n";

if( operation != "" )
{
output += operation + ": " + ratsResult.toString() + " (" + ratsResult.toDouble() + ")\n";

}

outputArea.setText( output );
}




public static void main( String args[] )
{
RationalTester rt = new RationalTester();

rt.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );

}

}

[jay smith]

I only get the error when I click on the "Divide" button. Nothing happens at all when I enter numbers into the text field and press enter or when I click on the other three buttons.

Thanks,
J

[Nigel Browne]

Catch the Aritmetic Exception which is caused by diving by zero.

[jay smith]

I haven't learned catches yet so I'm not going to attempt it.

I would like to know why I am getting this exception to begin with.

My constructor sets the denominator to 1.

Also, why am I not able to display output?

It seems like I am doing something wrong in the set methods.

It's things like this that keep me busy for hours.


[ July 20, 2005: Message edited by: jay smith ]
[ July 20, 2005: Message edited by: jay smith ]

[Nigel Browne]

Catch the Aritmetic Exception which is caused by diving by zero.

[jay smith]

I'm not sure I understand what you mean.

I have looked ahead in my textbook and I have seen catches, but I don't understand how they work.

Does that actually fix the problem that I am having in my code or does it just avoid the problem?

[Mark Spritzler]

OK here is something I see.

 
quotient.setNumer( getNumer() * ratValue.getDenom() );
 
// set denominator for the new Rational object by straight multiplying with the reciprocal of the second Rational
// ( denom1 * numer2 )
quotient.setDenom( getDenom() * ratValue.getNumer() );
 

in the setDenom, it is setting it to 0.

The tough thing about debugging, is that if there is code like qoutient.setDemon(Method call in here to get value), it is difficult to know the exact value returned. Now if the code was like

 
    int denom = getDenom();
    int ratValueNumerator = ratValue.getNumer();
    quotient.setDenom(denom * ratValueNumerator);
 

It is easy to System.out.println(denom); or System.out.println(ratValueNumerator) to make sure that they return values that you expect.

Also there is a check

 if( operation != "" ) 

This might not return the results you expect. It is better to use the equals method to check the value of Strings to one another.

I hope that helps a bit.

Mark

[Mark Spritzler]

Your results aren't showing because you setText on the outputArea JTextArea that you created, but never added it to the screen. Instead you put in

 
// create component for bottom panel and add them to bottom panel
resultLabel = new JLabel ( "Results" );
resultField = new JTextField( 7 );
 
middlePanel.add( resultLabel );
middlePanel.add( resultField );
 

resultField in the area you thought you'd put the outputArea reference.

Mark

[jay smith]

Mark,

You bring up a good point. If I assign 0 to numerator and 1 to denominator, then try to multiply by the reciprocal of that, then 0 ends up as the denominator.

That is another good point about using .equals to compare strings.

I do feel like I am learning this.

I am going to go to bed. It's 2:34am here and I have been going at this way too long. I'll be back on here tomorrow if I have any more questions about this program.

Thanks everyone!!!
J

[Mark Spritzler]

That is another good point about using .equals to compare strings.

Not that your code is failing right now, but if the left side was really null or "", then it would fail to work.

Mark

[Ernest Friedman-Hill]

The way you've written that event handler now, you are required to hit Enter after making every entry in a text field. If you don't, the values won't be transferred, and you'll have zeroes instead. There's the error you're seeing right there.

Moral of the story: make sure you show people the exact code you're running, or they won't be able to help!

[jay smith]

I'm am not sure how to fix the problem with the ActionListener. When I try to put the set methods in the else if statements, I get a StackOverflowError.

Below is my latest code. The Rational class has not changed.

Thanks,
J

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.DecimalFormat;
 

public class RationalTester extends JFrame implements ActionListener
{
private Rational rat1;
private Rational rat2;
private Rational ratsResult;
private String output = "";

private JButton addButton, subtractButton, multiplyButton, divideButton;

private JPanel topPanel, middlePanel;

private JLabel firstRatLabel, blank1Label, secondRatLabel, blank2Label, firstNumerLabel, firstDenomLabel, 
secondNumerLabel, secondDenomLabel;

private JTextField firstNumerField, firstDenomField, secondNumerField, secondDenomField;

private JTextArea outputArea;

private Container container;


public RationalTester()
{
super( "Rational Tester" );

container = getContentPane();
container.setBackground( Color.GREEN );

outputArea = new JTextArea();

// create panels
topPanel = new JPanel();
topPanel.setLayout( new GridLayout( 3, 4, 5, 5 ) );

middlePanel = new JPanel();
middlePanel.setLayout( new GridLayout( 3, 4, 5, 5 ) );

// create components for top panel and add them to top panel
firstRatLabel = new JLabel( "First Rational" );
blank1Label = new JLabel( "          " );
secondRatLabel = new JLabel( "Second Rational" );
blank2Label = new JLabel( "          " ); 

firstNumerLabel = new JLabel( "Numerator" );
firstNumerField = new JTextField( 5 );

firstDenomLabel = new JLabel( "Denominator" );
firstDenomField = new JTextField( 5 );

secondNumerLabel = new JLabel( "Numerator" );
secondNumerField = new JTextField( 5 );

secondDenomLabel = new JLabel( "Denominator" );
secondDenomField = new JTextField( 5 );

topPanel.add( firstRatLabel );
topPanel.add( blank1Label );
topPanel.add( secondRatLabel );
topPanel.add( blank2Label );

topPanel.add( firstNumerLabel );
topPanel.add( firstNumerField );
topPanel.add( secondNumerLabel );
topPanel.add( secondNumerField );

topPanel.add( firstDenomLabel );
topPanel.add( firstDenomField );
topPanel.add( secondDenomLabel );
topPanel.add( secondDenomField );

// create components for middle panel and add them to middle panel
addButton = new JButton( "Add Rationals" );
addButton.addActionListener( this );
addButton.setBackground( Color.ORANGE );

subtractButton = new JButton( "Subtract Rationals" );
subtractButton.addActionListener( this );
subtractButton.setBackground( Color.ORANGE );

multiplyButton = new JButton( "Multiply Rationals" );
multiplyButton.addActionListener( this );
multiplyButton.setBackground( Color.ORANGE );

divideButton = new JButton( "Divide Rationals" );
divideButton.addActionListener( this );
divideButton.setBackground( Color.ORANGE );

middlePanel.add( addButton );
middlePanel.add( subtractButton );
middlePanel.add( multiplyButton );
middlePanel.add( divideButton );
middlePanel.add( outputArea );

Container myContainer = getContentPane();
myContainer.setBackground( Color.GREEN );
myContainer.setLayout( new BorderLayout() );
myContainer.add( topPanel, BorderLayout.NORTH );
myContainer.add( middlePanel, BorderLayout.CENTER );

setSize( 450, 550 );
setVisible( true );

rat1 = new Rational();
rat2 = new Rational();

displayResult( "" );

}

public void actionPerformed( ActionEvent event )
{
reset();

if( event.getSource() == firstNumerField || event.getSource() == firstDenomField ||
event.getSource() == secondNumerField || event.getSource() == secondDenomField )
{

rat1.setNumer( Integer.parseInt( firstNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( firstDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

displayResult( "" );

}

else if( event.getSource() == addButton )
{
ratsResult = rat1.addRats( rat2 );
displayResult( "Sum" );

}

else if( event.getSource() == subtractButton )
{
ratsResult = rat1.subtractRats( rat2 );
displayResult( "Difference" );

}

else if( event.getSource() == multiplyButton )
{
ratsResult = rat1.multiplyRats( rat2 );
displayResult( "Product" );

}

else if( event.getSource() == divideButton )
{
ratsResult = rat1.divideRats( rat2 );////////////////////////////////////
displayResult( "Quotient" );

}

}

private void reset()
{
rat1 = new Rational();
rat2 = new Rational();
output = "";

}

private void displayResult( String operation )
{

output += "First Rational " + rat1.toString() + " (" + rat1.toDouble() + ")\n";

output += "Second Rational " + rat2.toString() + " (" + rat1.toDouble() + ")\n";

if ( operation.equals(  "" ) )
{


}

else
{

output += operation + ": " + ratsResult.toString() + " (" + ratsResult.toDouble() + ")\n";

}

outputArea.setText( output );
}

public static void main( String args[] )
{
RationalTester rt = new RationalTester();

rt.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );

}

}
 

[Ernest Friedman-Hill]

I would take these four lines:

rat1.setNumer( Integer.parseInt( firstNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( firstDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

out of the "if", put them into their own method, and call them from each one of the "else"s. There's no need to call it from the "if" but you could if you wanted.

But these lines don't handle the possibility that a text field contains not-a-number, so you're going to see NumberFormatExceptions all over the place. That little method would be a good place to put those handlers.

[jay smith]

OK, I have put the ActionListeners into inner classes. I am just trying a different approach to see if I can narrow down the problem.

Thanks,
J

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.DecimalFormat;
 

public class RationalTester extends JFrame
{
private Rational rat1;
private Rational rat2;
private Rational ratsResult;
private String output = "";

private JTextField firstNumerField, firstDenomField, secondNumerField, secondDenomField;

JTextArea outputArea;

public RationalTester()
{
super( "Rational Tester" );

Container container = getContentPane();


outputArea = new JTextArea();

// create panels
JPanel topPanel = new JPanel();
topPanel.setLayout( new GridLayout( 3, 4, 5, 5 ) );
topPanel.setBackground( Color.GREEN );

JPanel middlePanel = new JPanel();
middlePanel.setLayout( new GridLayout( 3, 4, 5, 5 ) );
middlePanel.setBackground( Color.GREEN );

// create components for top panel and add them to top panel
JLabel firstRatLabel = new JLabel( "First Rational" );
JLabel blank1Label = new JLabel( "          " );

JLabel secondRatLabel = new JLabel( "Second Rational" );
JLabel blank2Label = new JLabel( "          " ); 

JLabel firstNumerLabel = new JLabel( "Numerator" );
firstNumerField = new JTextField( 5 );

firstNumerField.addActionListener
(

new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( firstNumerField.getText() ) );

}

} // end anonymous inner class

); // end call to addActionListener

JLabel firstDenomLabel = new JLabel( "Denominator" );
firstDenomField = new JTextField( 5 );

firstDenomField.addActionListener
(

new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setDenom( Integer.parseInt( firstDenomField.getText() ) );

}

} // end anonymous inner class

); // end call to addActionListener


JLabel secondNumerLabel = new JLabel( "Numerator" );
secondNumerField = new JTextField( 5 );

secondNumerField.addActionListener
(

new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );

}

} // end anonymous inner class

); // end call to addActionListener


JLabel secondDenomLabel = new JLabel( "Denominator" );
secondDenomField = new JTextField( 5 );

secondDenomField.addActionListener
(

new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

}

} // end anonymous inner class

); // end call to addActionListener


topPanel.add( firstRatLabel );
topPanel.add( blank1Label );
topPanel.add( secondRatLabel );
topPanel.add( blank2Label );

topPanel.add( firstNumerLabel );
topPanel.add( firstNumerField );
topPanel.add( secondNumerLabel );
topPanel.add( secondNumerField );

topPanel.add( firstDenomLabel );
topPanel.add( firstDenomField );
topPanel.add( secondDenomLabel );
topPanel.add( secondDenomField );

// create components for middle panel and add them to middle panel
JButton addButton = new JButton( "Add Rationals" );
addButton.setBackground( Color.ORANGE );

addButton.addActionListener
(

new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( secondDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

ratsResult = rat1.addRats( rat2 );

displayResult( "Sum" );
}

} // end anonymous inner class

); // end call to addActionListener


JButton subtractButton = new JButton( "Subtract Rationals" );
subtractButton.setBackground( Color.ORANGE );

subtractButton.addActionListener
(

new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( secondDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

ratsResult = rat1.subtractRats( rat2 );

displayResult( "Difference" );
}

} // end anonymous inner class

); // end call to addActionListener

JButton multiplyButton = new JButton( "Multiply Rationals" );
multiplyButton.setBackground( Color.ORANGE );

multiplyButton.addActionListener
(

new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( secondDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

ratsResult = rat1.multiplyRats( rat2 );

displayResult( "Product" );
}

} // end anonymous inner class

); // end call to addActionListener

JButton divideButton = new JButton( "Divide Rationals" );
divideButton.setBackground( Color.ORANGE );

divideButton.addActionListener
(

new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( secondDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

ratsResult = rat1.divideRats( rat2 );

displayResult( "Quotient" );
}

} // end anonymous inner class

); // end call to addActionListener

middlePanel.add( addButton );
middlePanel.add( subtractButton );
middlePanel.add( multiplyButton );
middlePanel.add( divideButton );
middlePanel.add( outputArea );

Container myContainer = getContentPane();
myContainer.setBackground( Color.GREEN );
myContainer.setLayout( new BorderLayout() );
myContainer.add( topPanel, BorderLayout.NORTH );
myContainer.add( middlePanel, BorderLayout.CENTER );

setSize( 450, 550 );
setVisible( true );

rat1 = new Rational();
rat2 = new Rational();

displayResult( "" );

}

private void reset()
{
rat1 = new Rational();
rat2 = new Rational();
output = "";

}

private void displayResult( String operation )
{

output += "First Rational " + rat1.toString() + " (" + rat1.toDouble() + ")\n";

output += "Second Rational " + rat2.toString() + " (" + rat1.toDouble() + ")\n";

if ( operation.equals(  "" ) )
{


}

else
{

output += operation + ": " + ratsResult.toString() + " (" + ratsResult.toDouble() + ")\n";

}

outputArea.setText( output );
}

public static void main( String args[] )
{
RationalTester rt = new RationalTester();

rt.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );

}

}

[jay smith]

Thanks for the tip on NumberFormatExceptions. Here is what I am getting:

  
Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
at java.lang.Integer.parseInt(Integer.java:468)
at java.lang.Integer.parseInt(Integer.java:497)
at RationalTester$5.actionPerformed(RationalTester.java:155)

When I compile the code I just posted, it compiles fine.

When I run it and try to test it, the add and multiply buttons seem be working a little, but the subtract and divide buttons give me this:

Exception in thread "AWT-EventQueue-0" java.lang.StackOverflowError
at Rational.getGCD(Rational.java:225)   

But it repeats "at Rational.getGCD(Rational.java:225)" many times.

Thanks,
J
[ July 20, 2005: Message edited by: jay smith ]

[Ernest Friedman-Hill]

That's because getGCD() is recursive; it calls itself, and if it never stops calling itself, then the stack will overflow. You need to make sure that the exit condition will always occur -- i.e., that numer % denom always becomes zero (hint -- it clearly doesn't!)

[jay smith]

That makes sense. Thank you for pointing that out.

I have fixed the recursive gcd method. Here is the code.

  
public int getGCD(int numerValue, int denomValue)
{ 
if ( denomValue == 0 ) // if denomValue is zero return numerValue
{
return numerValue;

}// end if there is no remainder  
else
{ 
return getGCD( denomValue, ( numerValue % denomValue ) );

}// end else get gcd of denomValue and the remainder of ( numerValue / denomValue )
 

} // end method getGCD

I have updated the RationalTester class again. The code is below. The program is now accepting input, except it is assigning the value of the second rational to the first rational also.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.DecimalFormat;
 

public class RationalTester extends JFrame
{
private Rational rat1;
private Rational rat2;
private Rational ratsResult;
private String output = "";

private JTextField firstNumerField, firstDenomField, secondNumerField, secondDenomField;

JTextArea outputArea;

public RationalTester()
{
super( "Rational Tester" );

Container container = getContentPane();


outputArea = new JTextArea();

// create panels
JPanel topPanel = new JPanel();
topPanel.setLayout( new GridLayout( 3, 4, 5, 5 ) );
topPanel.setBackground( Color.GREEN );

JPanel middlePanel = new JPanel();
middlePanel.setLayout( new GridLayout( 3, 4, 5, 5 ) );
middlePanel.setBackground( Color.GREEN );

// create components for top panel and add them to top panel
JLabel firstRatLabel = new JLabel( "First Rational" );
JLabel blank1Label = new JLabel( "          " );

JLabel secondRatLabel = new JLabel( "Second Rational" );
JLabel blank2Label = new JLabel( "          " ); 

JLabel firstNumerLabel = new JLabel( "Numerator" );
firstNumerField = new JTextField( 5 );

firstNumerField.addActionListener
(

new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( firstNumerField.getText() ) );

}

} // end anonymous inner class

); // end call to addActionListener

JLabel firstDenomLabel = new JLabel( "Denominator" );
firstDenomField = new JTextField( 5 );

firstDenomField.addActionListener
(

new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setDenom( Integer.parseInt( firstDenomField.getText() ) );

}

} // end anonymous inner class

); // end call to addActionListener


JLabel secondNumerLabel = new JLabel( "Numerator" );
secondNumerField = new JTextField( 5 );

secondNumerField.addActionListener
(

new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );

}

} // end anonymous inner class

); // end call to addActionListener


JLabel secondDenomLabel = new JLabel( "Denominator" );
secondDenomField = new JTextField( 5 );

secondDenomField.addActionListener
(

new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

}

} // end anonymous inner class

); // end call to addActionListener


topPanel.add( firstRatLabel );
topPanel.add( blank1Label );
topPanel.add( secondRatLabel );
topPanel.add( blank2Label );

topPanel.add( firstNumerLabel );
topPanel.add( firstNumerField );
topPanel.add( secondNumerLabel );
topPanel.add( secondNumerField );

topPanel.add( firstDenomLabel );
topPanel.add( firstDenomField );
topPanel.add( secondDenomLabel );
topPanel.add( secondDenomField );

// create components for middle panel and add them to middle panel
JButton addButton = new JButton( "Add Rationals" );
addButton.setBackground( Color.ORANGE );

addButton.addActionListener
(

new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( secondDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

ratsResult = rat1.addRats( rat2 );

displayResult( "Sum" );
}

} // end anonymous inner class

); // end call to addActionListener


JButton subtractButton = new JButton( "Subtract Rationals" );
subtractButton.setBackground( Color.ORANGE );

subtractButton.addActionListener
(

new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( secondDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

ratsResult = rat1.subtractRats( rat2 );

displayResult( "Difference" );
}

} // end anonymous inner class

); // end call to addActionListener

JButton multiplyButton = new JButton( "Multiply Rationals" );
multiplyButton.setBackground( Color.ORANGE );

multiplyButton.addActionListener
(

new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( secondDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

ratsResult = rat1.multiplyRats( rat2 );

displayResult( "Product" );
}

} // end anonymous inner class

); // end call to addActionListener

JButton divideButton = new JButton( "Divide Rationals" );
divideButton.setBackground( Color.ORANGE );

divideButton.addActionListener
(

new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( secondDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

ratsResult = rat1.divideRats( rat2 );

displayResult( "Quotient" );
}

} // end anonymous inner class

); // end call to addActionListener

middlePanel.add( addButton );
middlePanel.add( subtractButton );
middlePanel.add( multiplyButton );
middlePanel.add( divideButton );
middlePanel.add( outputArea );

Container myContainer = getContentPane();
myContainer.setBackground( Color.GREEN );
myContainer.setLayout( new BorderLayout() );
myContainer.add( topPanel, BorderLayout.NORTH );
myContainer.add( middlePanel, BorderLayout.CENTER );

setSize( 450, 550 );
setVisible( true );

rat1 = new Rational();
rat2 = new Rational();

displayResult( "" );

}

private void reset()
{
rat1 = new Rational();
rat2 = new Rational();
output = "";

}

private void displayResult( String operation )
{

output += "First Rational:  " + rat1.toString() + " (" + rat1.toDouble() + ")\n";

output += "Second Rational:  " + rat2.toString() + " (" + rat2.toDouble() + ")\n";

if ( operation.equals(  "" ) )
{


}

else
{

output += operation + ":  " + ratsResult.toString() + " (" + ratsResult.toDouble() + ")\n";

}

outputArea.setText( output );
}

public static void main( String args[] )
{
RationalTester rt = new RationalTester();

rt.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );

}

}

[jay smith]

OK, still no luck. I have been through it a few times. I have made some changes. I would like to allow the user to specify the number of decimal points shown. Am I on the right path here?

I wonder why the value of rat2 is also getting assigned to rat1?

Thanks,
J

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.DecimalFormat;
 

public class RationalTester extends JFrame
{
private Rational rat1;
private Rational rat2;
private Rational ratsResult;
private String output = "";

private JTextField firstNumerField, firstDenomField, secondNumerField, secondDenomField, decimalPoints1Field, decimalPoints2Field;

JTextArea outputArea;

DecimalFormat userDigits = new DecimalFormat( );
int howManyDigits = 0;
int digits[];

public RationalTester()
{
super( "Rational Tester" );

Container container = getContentPane();

outputArea = new JTextArea();

// create panels
JPanel topPanel = new JPanel();
topPanel.setLayout( new GridLayout( 4, 4, 0, 3 ) );
topPanel.setBackground( new Color( 150, 255, 150 ) );


JPanel middlePanel = new JPanel();
middlePanel.setLayout( new GridLayout( 3, 4, 3, 3 ) );
middlePanel.setBackground( new Color( 150, 255, 150 ) );

// create components for top panel and add them to top panel
JLabel firstRatLabel = new JLabel( "     First Rational" );
firstRatLabel.setFont( new Font( "Monospaced", Font.BOLD, 18 ) );
JLabel blank1Label = new JLabel( "          " );

JLabel secondRatLabel = new JLabel( "     Second Rational" );
secondRatLabel.setFont( new Font( "Monospaced", Font.BOLD, 18 ) );
JLabel blank2Label = new JLabel( "          " ); 

JLabel blank3Label = new JLabel( "          " );
JLabel blank4Label = new JLabel( "          " );

JLabel firstNumerLabel = new JLabel( "     Numerator" );
firstNumerLabel.setFont( new Font( "Monospaced", Font.BOLD, 16 ) );
firstNumerField = new JTextField( 10 );

firstNumerField.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( firstNumerField.getText() ) );

}

} // end anonymous inner class

); // end call to addActionListener

JLabel firstDenomLabel = new JLabel( "     Denominator" );
firstDenomLabel.setFont( new Font( "Monospaced", Font.BOLD, 16 ) );
JTextField firstDenomField = new JTextField( 10 );

firstDenomField.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 

//rat1.setDenom( Integer.parseInt( firstDenomField.getText() ) );
//rat1.setDenom( Integer.parseInt( event.getActionCommand() ) );
//firstDenomField.getText();

}

} // end anonymous inner class

); // end call to addActionListener


JLabel secondNumerLabel = new JLabel( "     Numerator" );
secondNumerLabel.setFont( new Font( "Monospaced", Font.BOLD, 16 ) );
secondNumerField = new JTextField( 10 );

secondNumerField.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );

}

} // end anonymous inner class

); // end call to addActionListener


JLabel secondDenomLabel = new JLabel( "     Denominator" );
secondDenomLabel.setFont( new Font( "Monospaced", Font.BOLD, 16 ) );
secondDenomField = new JTextField( 10 );

secondDenomField.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

}

} // end anonymous inner class

); // end call to addActionListener

JLabel decimalPoints1Label = new JLabel( "     Decimal Points" );
decimalPoints1Label.setFont( new Font( "Monospaced", Font.BOLD, 16 ) );
decimalPoints1Field = new JTextField( 10 );

decimalPoints1Field.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
setDecimal( Integer.parseInt( decimalPoints1Field.getText() ) );

}

} // end anonymous inner class

); // end call to addActionListener

JLabel decimalPoints2Label = new JLabel( "     Decimal Points" );
decimalPoints2Label.setFont( new Font( "Monospaced", Font.BOLD, 16 ) );
decimalPoints2Field = new JTextField( 10 );

decimalPoints2Field.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
setDecimal( Integer.parseInt( decimalPoints2Field.getText() ) );
}

} // end anonymous inner class

); // end call to addActionListener


topPanel.add( firstRatLabel );
topPanel.add( blank1Label );
topPanel.add( secondRatLabel );
topPanel.add( blank2Label );

topPanel.add( firstNumerLabel );
topPanel.add( firstNumerField );
topPanel.add( secondNumerLabel );
topPanel.add( secondNumerField );

topPanel.add( firstDenomLabel );
topPanel.add( firstDenomField );

topPanel.add( secondDenomLabel );
topPanel.add( secondDenomField );

topPanel.add( decimalPoints1Label );
topPanel.add( decimalPoints1Field );

topPanel.add( decimalPoints2Label );
topPanel.add( decimalPoints2Field );



// create components for middle panel and add them to middle panel
JButton addButton = new JButton( "Add Rationals" );
addButton.setFont( new Font( "Monospaced", Font.BOLD, 18 ) );
addButton.setForeground( Color.CYAN );
addButton.setBackground( Color.BLACK );

addButton.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( secondDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

ratsResult = rat1.addRats( rat2 );

displayResult( "  Sum:  " );
}

} // end anonymous inner class

); // end call to addActionListener


JButton subtractButton = new JButton( "Subtract Rationals" );
subtractButton.setFont( new Font( "Monospaced", Font.BOLD, 18 ) );
subtractButton.setForeground( Color.MAGENTA );
subtractButton.setBackground( Color.BLACK );

subtractButton.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( secondDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

ratsResult = rat1.subtractRats( rat2 );

displayResult( "  Difference:  " );
}

} // end anonymous inner class

); // end call to addActionListener

JButton multiplyButton = new JButton( "Multiply Rationals" );
multiplyButton.setFont( new Font( "Monospaced", Font.BOLD, 18 ) );
multiplyButton.setForeground( Color.YELLOW );
multiplyButton.setBackground( Color.BLACK );

multiplyButton.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( secondDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

ratsResult = rat1.multiplyRats( rat2 );

displayResult( "  Product:  " );
}

} // end anonymous inner class

); // end call to addActionListener

JButton divideButton = new JButton( "Divide Rationals" );
divideButton.setFont( new Font( "Monospaced", Font.BOLD, 18 ) );
divideButton.setForeground( Color.ORANGE );
divideButton.setBackground( Color.BLACK );

divideButton.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( secondDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

ratsResult = rat1.divideRats( rat2 );

displayResult( "  Quotient:  " );
}

} // end anonymous inner class

); // end call to addActionListener

JButton clearButton = new JButton( "Clear" );
clearButton.setFont( new Font( "Monospaced", Font.BOLD, 18 ) );
clearButton.setForeground( Color.WHITE );
clearButton.setBackground( Color.BLACK );
clearButton.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
reset();

}

} // end anonymous inner class

); // end call to addActionListener

middlePanel.add( addButton );
middlePanel.add( subtractButton );
middlePanel.add( multiplyButton );
middlePanel.add( divideButton );
middlePanel.add( outputArea );
middlePanel.add( clearButton );

//middlePanel.setSize( 450, 500 );
//middlePanel.setVisible( true );


Container myContainer = getContentPane();
myContainer.setLayout( new BorderLayout() );
myContainer.add( topPanel, BorderLayout.NORTH );
myContainer.add( middlePanel, BorderLayout.CENTER );

setSize( 900, 750 );
setVisible( true );

rat1 = new Rational();
rat2 = new Rational();

displayResult( "" );

}


private void setDecimal( int decimalPointsValue )
{
howManyDigits = decimalPointsValue;
for( int i = 0; i < howManyDigits; i++ )
{
digits[i] = 0;

}

}


private void reset()
{
displayClear();
rat1 = new Rational();
rat2 = new Rational();
displayResult( "" );

}

private void displayResult( String operation )
{
int numer1 = rat1.getNumer();
int denom1 = rat1.getDenom();
int numer2 = rat2.getNumer();
int denom2 = rat2.getDenom();

output += "\n  First Rational Fraction:  " + numer1 + " / " + denom1 + "     Decimal:  " + userDigits.format( rat1.toDouble() ) + "\n";

output += "  Second Rational Fraction:  " + numer2 + " / " + denom2 + "     Decimal:  " + userDigits.format( rat2.toDouble() ) + "\n";

if( operation.equals( "  Sum:  " ) || operation.equals( "  Difference:  " ) || 
operation.equals( "  Product:  " ) || operation.equals( "  Quotient:  " ) )
{
output += operation +  ratsResult.toString() + "     Decimal:  " + ratsResult.toDouble() + "\n";

}

outputArea.setText( output );
}

private void displayClear()
{
output = "";
outputArea.setText( output );

}


public static void main( String args[] )
{
RationalTester rt = new RationalTester();

rt.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );

}

}
 

[jay smith]

I still cannot figure out what is wrong with my program. Also, I am getting this:

  
RationalTester.java:89: local variable firstDenomField is accessed from within inner class; needs to be declared final
rat1.setDenom( Integer.parseInt( firstDenomField.getText() ) );

Any help is extremely appreciated.

Thanks,
J

I did figure out how to let a user decide the number of decimal places.

I wrote this to help me with the decimal format part:

  
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.DecimalFormat;
 

public class UserDefinedDecimalFormat extends JApplet implements ActionListener
{
JLabel userInputLabel, outputLabel;
JTextField userInputField, outputField;

 
public void init()
{
Container container = getContentPane();
container.setLayout( new FlowLayout() );


userInputLabel = new JLabel( "Input number of decimal places: " );
container.add( userInputLabel );

userInputField = new JTextField( 10 );
container.add( userInputField );

userInputField.addActionListener( this );

outputLabel = new JLabel( "Output:  " );
container.add( outputLabel );

outputField = new JTextField( 10 );
outputField.setEditable( false );
container.add( outputField );

}

public void actionPerformed( ActionEvent event )
{
int decimalPlaces;

decimalPlaces = Integer.parseInt( userInputField.getText() );

String decimalPlacesArray[] = new String[decimalPlaces];

for( int counter = 0; counter < decimalPlacesArray.length; counter++ )
{
decimalPlacesArray[counter] = "0";
}



String decimalString = "";

for( int counter = 0; counter < decimalPlacesArray.length; counter++ )
{
decimalString += decimalPlacesArray[counter];
}



String userDigits = "." + decimalString;

outputField.setText( userDigits );
}
 
}

[jay smith]

OK, I feel dumb. I copied and pasted some of the code as I was writing the program and I forgot to change the names so the JTextFields were all named "second".

I still can't get the decimal format working. It looks like everything else is working fine.

Is anyone around to help?

Thanks,
J

  
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.DecimalFormat;
 

public class RationalTester extends JFrame
{
private Rational rat1 = new Rational();
private Rational rat2 = new Rational();
private Rational ratsResult;
private String output = "";
String userDigits1 = "";
String userDigits2 = "";

DecimalFormat userSpecifiedDigitFormat1 = new DecimalFormat( userDigits1 ); 
DecimalFormat userSpecifiedDigitFormat2 = new DecimalFormat( userDigits2 );

private JTextField firstNumerField, firstDenomField, 
secondNumerField, secondDenomField, 
decimalPoints1Field, decimalPoints2Field;

JTextArea outputArea;

public RationalTester()
{
super( "Rational Tester" );

Container container = getContentPane();

outputArea = new JTextArea();

// create panels
JPanel topPanel = new JPanel();
topPanel.setLayout( new GridLayout( 4, 4, 0, 3 ) );
topPanel.setBackground( new Color( 150, 255, 150 ) );

JPanel middlePanel = new JPanel();
middlePanel.setLayout( new GridLayout( 3, 4, 3, 3 ) );
middlePanel.setBackground( new Color( 150, 255, 150 ) );

// create components for top panel and add them to top panel
JLabel firstRatLabel = new JLabel( "     First Rational" );
firstRatLabel.setFont( new Font( "Monospaced", Font.BOLD, 18 ) );
JLabel blank1Label = new JLabel( "          " );

JLabel secondRatLabel = new JLabel( "     Second Rational" );
secondRatLabel.setFont( new Font( "Monospaced", Font.BOLD, 18 ) );
JLabel blank2Label = new JLabel( "          " ); 

JLabel blank3Label = new JLabel( "          " );
JLabel blank4Label = new JLabel( "          " );

JLabel firstNumerLabel = new JLabel( "     Numerator" );
firstNumerLabel.setFont( new Font( "Monospaced", Font.BOLD, 16 ) );
firstNumerField = new JTextField( 10 );

firstNumerField.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed(  ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( firstNumerField.getText() ) );

}

} // end anonymous inner class

); // end call to addActionListener

JLabel firstDenomLabel = new JLabel( "     Denominator" );
firstDenomLabel.setFont( new Font( "Monospaced", Font.BOLD, 16 ) );
firstDenomField = new JTextField( 10 );

firstDenomField.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
if( rat1.denomIsNotZero() == true )
{
rat1.setDenom( Integer.parseInt( firstDenomField.getText() ) );
}

}

} // end anonymous inner class

); // end call to addActionListener

JLabel secondNumerLabel = new JLabel( "     Numerator" );
secondNumerLabel.setFont( new Font( "Monospaced", Font.BOLD, 16 ) );
secondNumerField = new JTextField( 10 );

secondNumerField.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );

}

} // end anonymous inner class

); // end call to addActionListener

JLabel secondDenomLabel = new JLabel( "     Denominator" );
secondDenomLabel.setFont( new Font( "Monospaced", Font.BOLD, 16 ) );
secondDenomField = new JTextField( 10 );

secondDenomField.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
if( rat2.denomIsNotZero() == true )
{
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );
}

}

} // end anonymous inner class

); // end call to addActionListener

JLabel decimalPoints1Label = new JLabel( "     Decimal Points" );
decimalPoints1Label.setFont( new Font( "Monospaced", Font.BOLD, 16 ) );
decimalPoints1Field = new JTextField( 10 );

decimalPoints1Field.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
int decimalPlaces1 = 0;

//decimalPlaces1 = Integer.parseInt( decimalPoints1Field.getText() )  ;
setDecimalPlaces1( decimalPoints1Field.getText() );

String decimalPlaces1Array[] = new String[ decimalPlaces1 ];

for( int counter = 0; counter < decimalPlaces1Array.length; counter++ )
{
decimalPlaces1Array[ counter ] = "0";
}

String decimalString1 = "";

for( int counter = 0; counter < decimalPlaces1Array.length; counter++ )
{
decimalString1 += decimalPlaces1Array[ counter ];
}

userDigits1 = "." + decimalString1;

setDecimalPlaces1( userDigits1 );
}

} // end anonymous inner class

); // end call to addActionListener

JLabel decimalPoints2Label = new JLabel( "     Decimal Points" );
decimalPoints2Label.setFont( new Font( "Monospaced", Font.BOLD, 16 ) );
decimalPoints2Field = new JTextField( 10 );

decimalPoints2Field.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
int decimalPlaces2 = 0;

//decimalPlaces2 = Integer.parseInt( decimalPoints2Field.getText() );
setDecimalPlaces2( decimalPoints2Field.getText() );

String decimalPlaces2Array[] = new String[ decimalPlaces2 ];

for( int counter = 0; counter < decimalPlaces2Array.length; counter++ )
{
decimalPlaces2Array[ counter ] = "0";
}

String decimalString2 = "";

for( int counter = 0; counter < decimalPlaces2Array.length; counter++ )
{
decimalString2 += decimalPlaces2Array[ counter ];
}

userDigits2 = "." + decimalString2;

}

} // end anonymous inner class

); // end call to addActionListener

topPanel.add( firstRatLabel );
topPanel.add( blank1Label );
topPanel.add( secondRatLabel );
topPanel.add( blank2Label );

topPanel.add( firstNumerLabel );
topPanel.add( firstNumerField );
topPanel.add( secondNumerLabel );
topPanel.add( secondNumerField );

topPanel.add( firstDenomLabel );
topPanel.add( firstDenomField );

topPanel.add( secondDenomLabel );
topPanel.add( secondDenomField );

topPanel.add( decimalPoints1Label );
topPanel.add( decimalPoints1Field );

topPanel.add( decimalPoints2Label );
topPanel.add( decimalPoints2Field );

// create components for middle panel and add them to middle panel
JButton addButton = new JButton( "Add Rationals" );
addButton.setFont( new Font( "Monospaced", Font.BOLD, 18 ) );
addButton.setForeground( Color.CYAN );
addButton.setBackground( Color.BLACK );

addButton.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{
rat1.setNumer( Integer.parseInt( firstNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( firstDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

ratsResult = rat1.addRats( rat2 );

displayResult( "  Sum:  " ); 
   
}

} // end anonymous inner class

); // end call to addActionListener

JButton subtractButton = new JButton( "Subtract Rationals" );
subtractButton.setFont( new Font( "Monospaced", Font.BOLD, 18 ) );
subtractButton.setForeground( Color.MAGENTA );
subtractButton.setBackground( Color.BLACK );

subtractButton.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( firstNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( firstDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

ratsResult = rat1.subtractRats( rat2 );

displayResult( "  Difference:  " );  
}

} // end anonymous inner class

); // end call to addActionListener

JButton multiplyButton = new JButton( "Multiply Rationals" );
multiplyButton.setFont( new Font( "Monospaced", Font.BOLD, 18 ) );
multiplyButton.setForeground( Color.YELLOW );
multiplyButton.setBackground( Color.BLACK );

multiplyButton.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( firstNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( firstDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

ratsResult = rat1.multiplyRats( rat2 );

displayResult( "  Product:  " );  
}

} // end anonymous inner class

); // end call to addActionListener

JButton divideButton = new JButton( "Divide Rationals" );
divideButton.setFont( new Font( "Monospaced", Font.BOLD, 18 ) );
divideButton.setForeground( Color.ORANGE );
divideButton.setBackground( Color.BLACK );

divideButton.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
rat1.setNumer( Integer.parseInt( firstNumerField.getText() ) );
rat1.setDenom( Integer.parseInt( firstDenomField.getText() ) );
rat2.setNumer( Integer.parseInt( secondNumerField.getText() ) );
rat2.setDenom( Integer.parseInt( secondDenomField.getText() ) );

ratsResult = rat1.divideRats( rat2 );

displayResult( "  Quotient:  " ); 
}

} // end anonymous inner class

); // end call to addActionListener

JButton clearButton = new JButton( "Clear" );
clearButton.setFont( new Font( "Monospaced", Font.BOLD, 18 ) );
clearButton.setForeground( Color.WHITE );
clearButton.setBackground( Color.BLACK );
clearButton.addActionListener
(
new ActionListener()// anonymous inner class
{
// read value from user
public void actionPerformed( ActionEvent event )
{ 
reset();

}

} // end anonymous inner class

); // end call to addActionListener

middlePanel.add( addButton );
middlePanel.add( subtractButton );
middlePanel.add( multiplyButton );
middlePanel.add( divideButton );
middlePanel.add( outputArea );
middlePanel.add( clearButton );

Container myContainer = getContentPane();
myContainer.setLayout( new BorderLayout() );
myContainer.add( topPanel, BorderLayout.NORTH );
myContainer.add( middlePanel, BorderLayout.CENTER );

setSize( 900, 750 );
setVisible( true );

rat1 = new Rational();
rat2 = new Rational();

displayResult( "" );  

}

private void reset()
{
displayClear();
rat1 = new Rational();
rat2 = new Rational();
displayResult( "" );

}

public void setDecimalPlaces1( String decimalValue1 )
{
userDigits1 = decimalValue1;
}

public void setDecimalPlaces2( String decimalValue2 )
{
userDigits2 = decimalValue2;
}


private void displayResult( String operation )
{
int numer1 = rat1.getNumer();
int denom1 = rat1.getDenom();
int numer2 = rat2.getNumer();
int denom2 = rat2.getDenom();

output += "\n  First Rational Fraction:  " + numer1 + " / " + denom1 + "     Decimal:  " + userSpecifiedDigitFormat1.format( rat1.toDouble() ) + "\n";

output += "  Second Rational Fraction:  " + numer2 + " / " + denom2 + "     Decimal:  " + userSpecifiedDigitFormat2.format( rat2.toDouble() ) + "\n";

if( operation.equals( "  Sum:  " ) || operation.equals( "  Difference:  " ) || 
operation.equals( "  Product:  " ) || operation.equals( "  Quotient:  " ) )
{
output += operation +  ratsResult.toString() + "     Decimal:  " + ratsResult.toDouble() + "\n";

/////////////////
output += "uD1 " + userDigits1 + " " + "uD2 " + userDigits2; // to test for the values of decimal format
/////////////////
}

outputArea.setText( output );
}

private void displayClear()
{
output = "";
outputArea.setText( output );

}

public static void main( String args[] )
{
RationalTester rt = new RationalTester();  

rt.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );

}
}

[jay smith]

Any takers?

I really don't understand what I am doing wrong (or not doing at all) to allow the user to set the number of decimal places.

Thanks,
J

[eric elysia]

I still don't see what I am doing wrong.

J

[eric elysia]

OK, here is what I am working with.

import java.awt.*; 
import java.awt.event.*; 
import java.text.DecimalFormat; 
import java.lang.*; 
import javax.swing.*; 
 
public class DecimalFormatTester extends JFrame 
{ 
private int decimalPlaces; 
private DecimalFormat decimalFormat; 
private String userDigits = ""; 
private JTextField decimalFormatField; 
private String output = ""; 
JTextArea outputArea; 
public DecimalFormatTester() 
{ 
super( "Using Decimal Format" ); 
Container container = getContentPane(); 
container.setLayout( new FlowLayout() ); 
outputArea = new JTextArea(); 
JLabel decimalFormatLabel = new JLabel( " Decimal Points" ); 
decimalFormatField = new JTextField( 10 ); // Text fields don't post action events, so try binding on key events. 
decimalFormatField.addKeyListener(new KeyListener() 
{ 
public void keyTyped(KeyEvent e) 
{ 
} 
public void keyPressed(KeyEvent e) 
{ 
} 
public void keyReleased(KeyEvent e) 
{ 
if( e.getKeyCode() == KeyEvent.VK_ENTER ) 
{ 
System.out.println("Here"); 
setNumberOfDigits( Integer.parseInt( decimalFormatField.getText() ) ); 
output = decimalFormat.format( decimalPlaces ); 
displayOutput();
}
        }
});
container.add( decimalFormatLabel ); 
container.add( decimalFormatField ); 
container.add( outputArea ); 
setSize(420, 125 ); 
setVisible( true ); 
}
public void setNumberOfDigits(int nod) 
{ 
decimalPlaces = nod; 
String format = "#."; 
while( nod-- > 0 ) 
{ 
format = format + "0"; 
} 
decimalFormat = new DecimalFormat(format); 
// after this method is invoked, update the numbers being printed. 
}
/* 
private void displayResult( String operation ) 
{ 
output += "uD1 " + decimalPlaces; 
displayOutput(); 
} 
*/
private void displayOutput() 
{ 
outputArea.setText( output ); 
} 
public static void main( String args[] ) 
{ 
DecimalFormatTester dft = new DecimalFormatTester(); 
dft.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE ); 
} 
}

So to make sure I know what is going on, I changed

output = decimalFormat.format( Math.PI );

to

output = decimalFormat.format( decimalPlaces );

The program is displaying the number of zeros that the user inputs.
The program is also displaying the input number to the left of the decimal.

Is this just because the new decimal format has not been used to set the decimal place of any other variable yet?

I guess my question is that I do not understand how the actual number that the user inputs is being assigned to the left of the decimal.

DecimalFormat uses patterns.

In the code that you posted, the pattern is "#.".

So the # is the number that the user enters.

Is that right?

How do I use this to apply it to a sum of two fractions or something similar?
I am wanting to be able to let a user input two rational numbers (two numerators and two denominator), and enter the number of decimal places they prefer to see. Then the user can add, subtract, multiply, or divide the two fractions. I have everything working except for this part. I just want to understand how this works. Sorry for all the questions.

Thanks,
J