[citus]

Because when it is called, there is no value assigned to input so it is trying to add a JTextField Object to the number 32.

EDIT:
Read this

This post has been edited by citus: 12 April 2010 - 07:52 AM

[xor-logic]

I would hazard a guess that it's because you're trying to sum a textfield and a number literal. I think what you mean to do is add the value entered IN input to the number literal, which can be accomplished with input.getText(); . You'll need to parse it to an integer: Integer.parseInt(input.getText());. Warning: the code WILL throw an error if the input string is not a numeral. Use try-catch statements.

[pbl]

Topic title renamed
Please respect rule #5 of this forum
Give your topic a descriptive title, NOT "Help" or "Plz Help Me" or "I'm a noob"
"Jave help" is kind of useless in this forum

[japanir]

yes. better insert that code in the actionPerformed method.
also, make sure that what you type inside the JTextField is an int value (not double\String etc), or you'll get exceptions.
also, make sure you do type something inside.

[citus]

Yes, put it in actionPerformed. Did you read the link I posted above also? It should give you a better understanding of the methods of JTextField.

[japanir]

why all that code in the actionPerformed method?
type all code that you want to execute if the button1 is pressed inside the if block.
move all declaration of variables that you may use in other methods out of the actionPerformed.

[Dogstopper]

The reason it isn't displaying is this:

 output.setText(oneDigit.format(temp));

temp has no value...yet...move it below the claulation

Also, since you want the number to look like a decimal, you will want to Parse to a double, not an int:

public void actionPerformed(ActionEvent e){
            // as japanir said, these lines are useless...
            //input.getText();
            //input.addActionListener(this);

            double num;

            try {
                num = Double.parseDouble(input.getText());
            } catch (NumberFormatException e) {
                // Let user know that they must enter a double.  
                return; 
            }
            DecimalFormat oneDigit = new DecimalFormat("0.0");
                  
            // You should move your if to encompass all of this code instead.
            temp = 9.0 / 5.0 * (num + 32);    
           
            // Now that temp has a value, format it.
            output.setText(oneDigit.format(num));
          
  }

[sumit kothalikar]

guest, on 12 April 2010 - 06:36 AM, said:

<snip>

Edited byDogstopper: useless post interrupted the flow of posts.

This post has been edited by Dogstopper: 13 April 2010 - 03:03 PM

[Dogstopper]

sumit kothalikar, please don't quote someone's post and have NOTHING to say about it... thanks...

[Dogstopper]

You keep randomly adding anonymous elements to your Applet. when you say add(new JLabel());, there is no way to reference that JLabel later. You have to instantiate and add elements that you can use later. Also, name the exception something other than e:

    import java.awt.*; 
    import java.applet.*; 
    import java.awt.event.*;
    import javax.swing.*;

import java.text.DecimalFormat;

    public class RMH12_01 extends Applet implements ActionListener{

            
            
            JLabel output;
            double temp;
            Button button1;
            JTextField input;
            

      public void init()                       
      {  
             
        button1= new Button("");   
        button1.addActionListener(this);
        add(button1);
        input = new JTextField(10);
        add( input);
        output= new JLabel("");
        add(output);
        
        
       
      }
      
      public void actionPerformed(ActionEvent e){ //// also i am receiving an error on this line 
               
        double num;
        if(e.getSource() == button1){
            try {
            	num = Double.parseDouble(input.getText());
            } catch (NumberFormatException exception) {
            	JOptionPane.showMessageDialog(this, "Has to be a double");
            	return; 
            }
            DecimalFormat oneDigit = new DecimalFormat("0.0");
          
            temp = (9.0 / 5.0) * (num + 32);
                      
            output.setText(oneDigit.format(temp));
         }
          
      }
      
   }

[macosxnerd101]

dogstopper said:

You have to instantiate and add elements that you can use later.

I'd like to expand on what Dogstopper said. If you want to use Components later, then you really should declare them before using them, as it is a pain to hunt through your Container to obtain them. Nine out of ten times, you will not have a Component if you do not plan on modifying its display. Even if you are not modifying it in this class or this program, you may want to extend the class and use those Components in the subclass. Anonymous objects inhibit this.