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Thread: Java Swing

  1. #1
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    Default Java Swing

    I am learning java swing and the following code is not working. What am I doing wrong?

    public void actionPerformed(ActionEvent ae)
    	{
    		if(ae.getActionCommand().equals("Convert"))
    		{
    			if(Cel)
    			{
    			int jml = Integer.parseInt(Cel.getText());
    			int result = jml * 9/5 + 32;
    			Fah.setText(Integer.toString(result));
    			}
    			else
    			{
    				int jml = Integer.parseInt(Fah.getText());
    				int result = (jml - 32) * 5/9;
    				Fah.setText(Integer.toString(result));
    			}
    		}
    		else
    		{
    			Cel.setText("");
    			Fah.setText("");
    		}
    	}


     
    import java.awt.FlowLayout;
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
     
    import javax.swing.*;
    import javax.swing.border.Border;
     
    public class TempConvertor extends JFrame implements ActionListener
    {
    	JButton Convert;
    	JButton Reset;
    	JTextField Cel;
    	JTextField Fah;
    	JLabel CelLbl;
    	JLabel farenheight;
     
    	TempConvertor()
    	{
    		JFrame j = new JFrame("Temp Convertor");
    		j.setSize(200,175);
    		j.setResizable(false);
    		j.setLayout(new FlowLayout());
    		j.setDefaultCloseOperation(EXIT_ON_CLOSE);
     
    		//create buttons
    		Convert = new JButton("Convert");
    		Reset = new JButton("Reset");
     
    		Convert.addActionListener(this);
    		Reset.addActionListener(this);
     
    		//create labels
    		CelLbl = new JLabel("Celsius");
    		farenheight = new JLabel("Farenheight");
     
    		CelLbl.setVerticalAlignment(SwingConstants.BOTTOM);
    		farenheight.setVerticalAlignment(SwingConstants.BOTTOM);
    		Border border = BorderFactory.createEtchedBorder();
    		CelLbl.setBorder(border);
    		farenheight.setBorder(border);
     
    		JPanel cp = ((JPanel) j.getContentPane());
    		cp.setBorder(BorderFactory.createEmptyBorder(4,4,4,4));
     
    		//create text fields
    		Cel = new JTextField(5);
    		Fah = new JTextField(5);
     
    		Cel.setActionCommand("Cel");
    		Fah.setActionCommand("Fah");
     
    		//add TextFields
    		j.add(CelLbl);
    		j.add(Cel);
    		j.add(farenheight);//label
     
    		j.add(Fah);
     
    		//add Buttons
    		j.add(Convert);
    		j.add(Reset);
     
    		j.setVisible(true);	
    	}
     
    	public void actionPerformed(ActionEvent ae)
    	{
    		if(ae.getActionCommand().equals("Convert"))
    		{
    			if(Cel)
    			{
    			int jml = Integer.parseInt(Cel.getText());
    			int result = jml * 9/5 + 32;
    			Fah.setText(Integer.toString(result));
    			}
    			else
    			{
    				int jml = Integer.parseInt(Fah.getText());
    				int result = (jml - 32) * 5/9;
    				Fah.setText(Integer.toString(result));
    			}
    		}
    		else
    		{
    			Cel.setText("");
    			Fah.setText("");
    		}
    	}
     
     
    	public static void main(String[] args)
    	{
    		new TempConvertor();
    	}
    }


  2. #2
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    Default Re: Java Swing

    the following code is not working
    Define 'not working'. Does it compile? Are there exceptions? Does it misbehave, and if so, how? Without supplying more details we're left guessing

  3. #3
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    Default Re: Java Swing

    Most likely not your main problem, but I assume this is not what you intend: 9/5 and 5/9
    Those produce 1 and 0, respectfully. You are doing something called "Integer Division". To put it simply: 9/5 should equal 1.8, but an int divided by an int makes another int, not a double (ints have no decimal places, doubles have decimal places). In order to get a double value, at least one of the values need to be a double. To make one of those a double, just add a decimal point to one of them.
    So, in java:
    9/5 = 1
    9.0/5 = 1.8
    9/5.0 = 1.8
    9.0/5.0 = 1.8
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