HELP?! making an application w/static void main(String []args)

[Rob Michaelson]

Hello all,
I am having difficulty understanding how to make an app with statis void main. here are my instructions (And then my code - should I go to the Intermediate Forum? please let me know - this may be easy but I am knew to Java blah blah blah)

Create an Application from this Class
Add the method to this class to make it an application.
Within this method, instantiate an new object.
If there are any parameters provided on the command line when the application is started, use the parameters to �prefill� the list of String values.
Test your work. You can either test this using BlueJ and providing a array aggregate value, or using a command prompt and invoking the application using the following:
here's my code so far:

import dLibrary.*;
import java.awt.Color;
import java.awt.List;
import java.util.Iterator;
/** 
 * 
 * @author Rob 
 * @version 8/18/03 
 **/ 
 
 public class PhrasesII extends A3ButtonHandler
 
 {      
     private java.awt.List display;      
     private java.util.List entries;      
     private ATextField textHere;      
     private ALabel status;      
     private ALabel listOstrings;      
     private ALabel inputString;      
     private A3ButtonWindow win;        
 
    /** 
     * Constructor for PhrasesII    
     *  
     */    
     
     public PhrasesII()     
    {                
         win = new A3ButtonWindow(this);        
         win.setLeftText("Store");        
         win.setMidText("Display");        
         win.setRightText("Discard");
     
         entries = new java.util.Vector();        
         textHere = new ATextField(50,420,200,25);        
         textHere.place(win);        
         textHere.setFontSize(12);
         
         status = new ALabel(200,380,400,20);        
         status.place(win);        
         status.setFontSize(12);
         
         display = new java.awt.List();        
         display.setLocation(200, 100);        
         display.setSize(200, 250);        
         display.setBackground(Color.lightGray);        
         win.add(display, 0);
         
         inputString = new ALabel(50,400,200,25);        
         inputString.setText("Input String:");        
         inputString.place(win);        
         inputString.setFontSize(12);
         
         listOstrings = new ALabel(250,80,200,25);        
         listOstrings.setText("List of Strings");        
         listOstrings.place(win);        
         listOstrings.setFontSize(12);         
         win.repaint();    
     }    
     
     /**     
      * Set up a status message    
      */    
 
 
     private void status(String s)    
     {        
         status.setColor(Color.black);        
         status.setText(s);        
     }    
     
     /** 
      * Set up status message color red     
      */    
  
  
      private void status(Color c, String s)    
      {        
          status.setColor(c);        
          status.setText(s);    
      }        
      
      public void leftAction()   
      {                
          if(textHere.getText().length()>0)        
          {            
          entries.add(textHere.getText());            
          status("There are " + entries.size() + " entries in the list.");        
          }        
          else            
          status(Color.red,"Input field cannot be blank");                    
          textHere.setText("");    
          textHere.requestFocus();    
          }        
          public void midAction()         
          { 
          for (Iterator it = entries.iterator(); 
          it.hasNext() :wink:   
          {    
          String line = (String) it.next();    
          display.add(line);
          status(entries.size() + " items displayed");    
          textHere.requestFocus();
          }       
      }               
      
      
      public void rightAction()    
      {        
          entries.clear();        
          display.removeAll();        
          textHere.setText("");        
          status("There are " + entries.size() + " items in the list");            
          textHere.requestFocus();    
      }      
      
// <<<<<<<<<<<HERE>>>>>>>>>>>>>>>>>>>>>>>
public static void main(String[] args)    
      {        
         if(args.length !=2)
          System.out.println("testing" + i + " testing " + args[i]);
         return;
      }
      int val1,val2;
      val1 = Integer.parseInt(args[0]);
      val2 = Integer.parseInt(args[1]);
      new Phrases (val1,val2);
      }
  }

Thanks
Rob

[Joel McNary]

Several things here:

100: public static void main(String[] args)    
101: {        
102:     if(args.length !=2)
103:         System.out.println("testing" + i + " testing " + args[ i ]);
104:     return;
105: }
106: int val1,val2;
107: val1 = Integer.parseInt(args[0]);
108: val2 = Integer.parseInt(args[1]);
109: new Phrases (val1,val2);
110: }

(Note: the line numbers may not be actualy line numbers, they are just used for convenience here)
Line 102:
It strikes me that you forgot to include an open curly-brace at the end of the line. As such, the close-curly brace in line 105 will close the main method, not the if statement. Anyting after line 105 will give you a compilation error.
While, of course, yyour style may differ, it is for this reason that I advocate always using curly braces around single-line if/for/while blocks.
Line 103:
Where is the variable i coming from?
Line 109:
Should you not be creating a new PhrasesII object, instead of a Phrases object?
Also, I do not see where you have a constructor that takes two ints as arguments.
For that matter, why are you parsing Integers? It strikes me that the exercise instructions specified to use Strings. Also, why are you checking the args[] length in line 102? Is this for testing purposes, or what is going on here?
Give it another go round with these suggestions, and if you still have probelms, we're here to help....

[Rob Michaelson]

How about this?

import dLibrary.*;
import java.awt.Color;
import java.awt.List;
import java.util.Iterator;
/** 
 * 
 * @author Rob Michaelson  
 * @version 8/18/03 
 **/ 
 
 public class PhrasesII extends A3ButtonHandler
 
 {      
     private java.awt.List display;      
     private java.util.List entries;      
     private ATextField textHere;      
     private ALabel status;      
     private ALabel listOstrings;      
     private ALabel inputString;      
     private A3ButtonWindow win;        
 
    /** 
     * Constructor for PhrasesII    
     *  
     */    
     
     public PhrasesII(int val1, int val2)     
    {                
         win = new A3ButtonWindow(this);        
         win.setLeftText("Store");        
         win.setMidText("Display");        
         win.setRightText("Discard");
     
         entries = new java.util.Vector();        
         textHere = new ATextField(50,420,200,25);        
         textHere.place(win);        
         textHere.setFontSize(12);
         
         status = new ALabel(200,380,400,20);        
         status.place(win);        
         status.setFontSize(12);
         
         display = new java.awt.List();        
         display.setLocation(200, 100);        
         display.setSize(200, 250);        
         display.setBackground(Color.lightGray);        
         win.add(display, 0);
         
         inputString = new ALabel(50,400,200,25);        
         inputString.setText("Input String:");        
         inputString.place(win);        
         inputString.setFontSize(12);
         
         listOstrings = new ALabel(250,80,200,25);        
         listOstrings.setText("List of Strings");        
         listOstrings.place(win);        
         listOstrings.setFontSize(12);         
         win.repaint();    
     }    
     
     /**     
      * Set up a status message    
      */    
 
 
     private void status(String s)    
     {        
         status.setColor(Color.black);        
         status.setText(s);        
     }    
     
     /** 
      * Set up status message color red     
      */    
  
  
      private void status(Color c, String s)    
      {        
          status.setColor(c);        
          status.setText(s);    
      }        
      
      public void leftAction()   
      {                
          if(textHere.getText().length()>0)        
          {            
          entries.add(textHere.getText());            
          status("There are " + entries.size() + " entries in the list.");        
          }        
          else            
          status(Color.red,"Input field cannot be blank");                    
          textHere.setText("");    
          textHere.requestFocus();    
          }        
          public void midAction()         
          { 
          for (Iterator it = entries.iterator(); 
          it.hasNext() :wink:   
          {    
          String line = (String) it.next();    
          display.add(line);
          status(entries.size() + " items displayed");    
          textHere.requestFocus();
          }       
      }               
      
      
      public void rightAction()    
      {        
          entries.clear();        
          display.removeAll();        
          textHere.setText("");        
          status("There are " + entries.size() + " items in the list");            
          textHere.requestFocus();    
      }      
    public static void main(String[] args) 
    {
    
    if(args.length !=2) 
    { 
  
   System.out.println("usage: PhrasesII <int1> <int2>"); 
    
    return;    
    }    
    int val1;    
    int val2;    
    val1 = Integer.parseInt(args[0]);    
    val2 = Integer.parseInt(args[1]);    
    new PhrasesII (val1,val2);
      }
  }

no syntax errors -
thanks
Rob

[Joel McNary]

That looks better syntactically; the question is, does the program do what the assignment asks?

If there are any parameters provided on the command line when the application is started, use the parameters to �prefill� the list of String values.

So ask yourself, "Does my program accomplish this?"
Run
java PhasesII This is a Test
at the command line and see what happens.
Hint: (If I'm reading the instructions correctly) You should somewhere pass a java.util.List of Strings to your PhasesII object and use that to initialize the entries member variable.