Help with creating GUI Error Messages.

[Ryan Childs]

I have an assignment where I must modify my code to:
A: If the weight of an object is greater than 99999 your code should print a GUI driven error message, and force the user to reenter the weight of the object.
B: If a user enters a negative weight, your code should display a GUI warning message.

My original code is:

package guiprogrampart2;

import javax.swing.*;
 


    public class GuiProgramPart2{

    
    public static void main(String[] args) {
        
            String[] name = new String[4]; 
            double[] weight = new double[4];
            Weight [] object = new Weight[4];
  
            for (int i = 0; i <object.length; i++)
            {

            String ObjectName = JOptionPane.showInputDialog("What is the Objects name?"); 
            int ObjectWeight = Integer.parseInt(JOptionPane.showInputDialog( "What is the Objects Weight?"));    
                
            object[i] = new Weight();
            object[i].setObjectName(ObjectName);
            object[i].setWeight(ObjectWeight);

                
                       // display result in a JOptionPane message dialog
            JOptionPane.showMessageDialog( null, "The " + ObjectName + " weighs " + ObjectWeight + " lbs on Earth" + "\nOn the Moon it weighs " + object[i].calcMoon() + " lbs "+ "\nOn Mercury it weighs " + object[i].calcMercury() + " lbs "+ "\nOn Jupiter it weighs " + object[i].calcJupiter() + " lbs ","Weight of Object", JOptionPane.PLAIN_MESSAGE );
            }             
    }
 }
   

    

Not sure if its needed, but the Weight class is:

package guiprogrampart2;

public class Weight {
    
        double weight;
        String ObjectName;
        double Mercury = .378;
        double Moon = .166;
        double Jupiter = 2.364;
        
        double calculation;
        public Weight()
        {
            weight = 0;
            calculation = 0;
        }
        
        public void setObjectName (String object)
        {
            this.ObjectName = object;
        }
        public void setWeight (double input)
        {
            this.weight = input;
        }
        public double calcMercury()
        {
            calculation = weight * Mercury;
            return(calculation);
        }
        public double calcMoon()
        {
            calculation = weight * Moon;
            return(calculation);
        }
        public double calcJupiter()
        {
            calculation = weight * Jupiter;
            return(calculation);
        }
        
} 

I thought in order to add the error message pop ups it would require an IF statement. I came up with:

                if (ObjectWeight > 99999){
                    JOptionPane.showInputDialog("Please enter a number less than 99,999.");                 
                }
                if (ObjectWeight < 0){
                    JOptionPane.showMessageDialog(null, "Number must be positive!", "Error", JOptionPane.ERROR_MESSAGE);
                }

The entire code with the addition looks like:

package guiprogrampart2;

import javax.swing.*;
 


    public class GuiProgramPart2{

    
    public static void main(String[] args) {
        
            String[] name = new String[4]; 
            double[] weight = new double[4];
            Weight [] object = new Weight[4];
  
            for (int i = 0; i <object.length; i++)
            {

            String ObjectName = JOptionPane.showInputDialog("What is the Objects name?"); 
            int ObjectWeight = Integer.parseInt(JOptionPane.showInputDialog( "What is the Objects Weight?"));    

                 if (ObjectWeight > 99999){
                    JOptionPane.showInputDialog("Please enter a number less than 99,999.");                 
                }
                if (ObjectWeight < 0){
                    JOptionPane.showMessageDialog(null, "Number must be positive!", "Error", JOptionPane.ERROR_MESSAGE);
                }

            object[i] = new Weight();
            object[i].setObjectName(ObjectName);
            object[i].setWeight(ObjectWeight);

                
                       // display result in a JOptionPane message dialog
            JOptionPane.showMessageDialog( null, "The " + ObjectName + " weighs " + ObjectWeight + " lbs on Earth" + "\nOn the Moon it weighs " + object[i].calcMoon() + " lbs "+ "\nOn Mercury it weighs " + object[i].calcMercury() + " lbs "+ "\nOn Jupiter it weighs " + object[i].calcJupiter() + " lbs ","Weight of Object", JOptionPane.PLAIN_MESSAGE );
            }             
    }
 }

When I run the program it runs just the original program. It does not recognize if I enter a number higher than 99,999 or less than 0 and performs the calculations as normal. I am completely unsure as to what I am missing. Any help pointing me in the right direction would be greatly appreciated.

[Greg Brannon]

Did you not understand my suggestion in the other forum? If not, please describe your confusion and ask additional questions in the original post.

Edit:

My suggestion from the other forum:

You need some kind of loop to repeat the request for the object's weight if the user's entry is incorrect, something like:

do
{
    // error = false

    // get the weight

    // check the weight

    // if the weight is too much, error = true

    // if the weight is too little, error = true
}
while ( error );

[Ryan Childs]

Haha, no, just thanks to the Wifey I lost browser history and could for the life of me not recall the site.

Anyways, you suggested the do-while loop.

I was working on that and could not figure out the proper way to construct it.

I understand I need to have for lets say the "A" portion:

do {
JOptionPane.showMessageDialog(null, "Please enter a number lower than 99,999", "Error", JOptionPane.ERROR_MESSAGE);

}while(ObjectWeight > 99999);

However the bit about setting parts to false and true completely lost me. Also I am unsure where the do-while loop is suppose to fit in the original code.

Again my bad on switching to a different site, awesome that you are here as well though! (would love the name of that other site too)

[Greg Brannon]

You have the construct of the do/while loop correct, and you could do it the way you've coded. I suggested using an error flag, a boolean called 'error', so that multiple conditions could be tested in a single loop with the minimum or simplest (in my mind) code. Since you want to test for both greater than and less than a certain amount, your while statement should look like:

while( ObjectWeight > 99999 || ObjectWeight < 0 );

so that the do loop will continue to execute, asking the user for the object's weight, until a correct number is entered.

I'll PM you the other site.

[Michael Dunn]

perhaps you could work (compare notes) with this poster

http://www.coderanch.com/t/565460/GUI/java/Help-GUI-assignment