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Thread: Stuck in converting meters in milimeters

  1. #1
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    Default Stuck in converting meters in milimeters

    here's my code:

    import javax.swing.*;
    import java.awt.*;
    import java.awt.event.*;
    import java.util.*;
     
    public class Milimetri extends JFrame {
     
    private JPanel p1 = new JPanel(new FlowLayout(FlowLayout.LEFT));
    private JPanel p2 = new JPanel(new FlowLayout(FlowLayout.LEFT));
    private JPanel p3 = new JPanel(new FlowLayout(FlowLayout.LEFT));
     
    private JLabel e1 = new JLabel("Meters");
    private JLabel e2 = new JLabel("Milimeters:");
     
    private JTextField t1 = new JTextField(20);
    private JTextField t2 = new JTextField(20);
     
    private JButton b1 = new JButton("Result");
     
    public Milimetri(){
    super("Metri in Centimetri");
    setLayout(new GridLayout(3,1));
    add(p1); add(p2); add(p3);
     
    p1.add(e1);p1.add(t1);
    p2.add(e2);p2.add(t2);
    p3.add(b1);
     
    pack();
    setResizable(false);
    setLocationRelativeTo(null);
    setVisible(true);
     
    b1.addActionListener(
    new ActionListener(){
    public void actionPerformed(ActionEvent ev){
    double meters = Double.parseDouble(t1.getText());
    String milimeters = t2.setText();
     
    }
     
    }
    );
     
    }

    When i write a value in meters ..and press the button b1 to show me a value in milimeters...but i don't know what to do!

    Pls help!

    have a nice day!

    PS: i hope i posted correctly


  2. #2
    Crazy Cat Lady KevinWorkman's Avatar
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    Default Re: Stuck in converting meters in milimeters

    Which part of this is giving you trouble? Can you write a standalone program that simple converts from meters to millimeters using hardcoded double values? Can you write a standalone program that converts a String to a double? Can you write a standalone program that prints out the String from a text component one a gui?

    When you have all of those pieces working separately, then you should start combining them. And if you get stuck on a specific part, you can ask a specific question about that part. Good luck.
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  3. #3
    Member andbin's Avatar
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    Default Re: Stuck in converting meters in milimeters

    Quote Originally Posted by axeleesh View Post
    String milimeters = t2.setText();
    This is wrong. You have a double value, convert it to String (it's sufficient the string concatenation operator adding to "" or more cleanly the String.valueOf method) and then invoke setText passing that String.

    P.S.
    1) Your code is not well (not at all) indented. Please fix in the post and also in your original code if it is as I see here now.
    2) Please, try to give "good" names to variables, not p1, e1, b1, etc...
    Andrea, www.andbin.net SCJP 5 (91%) SCWCD 5 (94%)

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  4. #4
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    Default Re: Stuck in converting meters in milimeters

    You had it nearly there, you needed to convert the meters to millimetres by multiplying by 1000, save the result in a double variable.

    Then set the text box value using setText() to the double value in the millimetres variable but you need to convert it back to a string first by using Double.toString().


    Please see my quick mock up below (this works):

    package milimetri;
     
    import javax.swing.*;
    import java.awt.*;
    import java.awt.event.*;
     
    public class Milimetri extends JFrame
    {
     
        private JPanel p1 = new JPanel(new FlowLayout(FlowLayout.LEFT));
        private JPanel p2 = new JPanel(new FlowLayout(FlowLayout.LEFT));
        private JPanel p3 = new JPanel(new FlowLayout(FlowLayout.LEFT));
     
        private JLabel e1 = new JLabel("Meters");
        private JLabel e2 = new JLabel("Milimeters:");
     
        private JTextField t1 = new JTextField(20);
        private JTextField t2 = new JTextField(20);
     
        private JButton b1 = new JButton("Result");
     
        public Milimetri()
        {
            super("Metri in Centimetri");
            setLayout(new GridLayout(3,1));
            add(p1);
            add(p2);
            add(p3);
     
            p1.add(e1);
            p1.add(t1);
            p2.add(e2);
            p2.add(t2);
            p3.add(b1);
     
            pack();
            setResizable(false);
            setLocationRelativeTo(null);
            setVisible(true);
     
            b1.addActionListener(new ActionListener()
                                     {
                                        public void actionPerformed(ActionEvent ev)
                                        {
                                            double meters = Double.parseDouble(t1.getText());
                                            double milimeters = meters * 1000;
                                            t2.setText(Double.toString(milimeters));
                                        }
     
                                     }
            );
     
        }
     
        public static void main(String args[])
        {
            Milimetri m = new Milimetri();
        }
     
    }

  5. #5
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    Default Re: Stuck in converting meters in milimeters

    Thank you for your help! i understand now what i have to do!

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