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Thread: how to delete single string from JTextField??

  1. #1
    raffs03 is offline Member
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    Default Help me understand this..

    Java Code:
    import java.awt.*;
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    import javax.swing.*;
    
    public class calcSample extends JFrame{
        
        public calcSample(){
            setVisible(true);
            setSize(400,400);
            setDefaultCloseOperation(EXIT_ON_CLOSE);
            setLocationRelativeTo(null);
            setLayout(new GridLayout(3,1));
         txt1 = new JTextField();
         btnDel = new JButton("Del");
         btnOne = new JButton("1");
         txt1.setEditable(false);
         btnDel.addActionListener(new ActionListener() {
    
                @Override
                public void actionPerformed(ActionEvent e) {
                    String delString1 = txt1.getText(); 
          StringBuilder stBuild = new StringBuilder(txt1);
               stBuild.deleteCharAt(i);
               txt1.setText(stBuild.toString());
               System.out.println("Index "+i);
               System.out.println("String Length "+ delString1.length());
               System.out.println("String Edited " + String.valueOf(stBuild));
            }});
         btnOne.addActionListener(new ActionListener() {
    
                @Override
                public void actionPerformed(ActionEvent e) {
                    String One = txt1.getText();
                    txt1.setText(One+1);
                }
            });
         
         add(txt1);
         add(btnDel);
         add(btnOne);
        }
        public static void main(String[]args){
            new calcSample();
        }
        private JTextField txt1;
        private JButton btnDel,btnOne;
        
    }
    Output:
    Java Code:
    1111
    After clicking Del
    111
    click Del again
    11
    and so on.....
    but i don't understand how this code works:
    Java Code:
     btnDel.addActionListener(new ActionListener() {
    
                @Override
                public void actionPerformed(ActionEvent e) {
                    String delString1 = txt1.getText(); 
          StringBuilder stBuild = new StringBuilder(txt1);
               stBuild.deleteCharAt(i);
               txt1.setText(stBuild.toString());
               System.out.println("Index "+i);
               System.out.println("String Length "+ delString1.length());
               System.out.println("String Edited " + String.valueOf(stBuild));
            }});
    the println code is for the debugging.
    Can someone tell me how this code deleted the last character of the inputted String w/ for loop simulation please :D
    because for loop is
    Last edited by raffs03; 07-03-2013 at 04:23 AM.

  2. #2
    wsaryada is offline Senior Member
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    Default Re: how to delete single string from JTextField??

    The deleteCharAt(int index) method of the StringBuilder object delete the character at the specified index. But I didn't see any variable "i" declared in your code.

  3. #3
    JosAH's Avatar
    JosAH is online now Moderator
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    Default Re: Help me understand this..

    Quote Originally Posted by raffs03 View Post
    but i don't understand how this code works:
    I think it is ok to assume that you didn't write the code yourself; why don't you ask the author(s) of the code what it means and how it works?

    kind regards,

    Jos
    DarrylBurke and MR bruto like this.
    The only person who got everything done by Friday was Robinson Crusoe.

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