how do I filter what I entered in the JTextField and display the filtered result?

Question

package javaisnotbannana;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.*;
import javax.swing.*;
public class  Javaisnotbannana{

    public static void main(String[] args) { 
        window();
    }       
////////////////////////////////////////////////////
public static void window()
    {
     JFrame window= new JFrame();
     JPanel jp = new JPanel();
     JLabel jl = new JLabel();
     JTextField jt = new JTextField(30);
     JButton jb = new JButton("Enter");
     window.setTitle("ThisisTitleofWindow");
     window.setVisible(true);
     window.setSize(500, 500);
     window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     //textfield
     jp.add(jt);
     jt.addActionListener(new ActionListener()
     {
     public void actionPerformed(ActionEvent e)
     {
     String inoutt = jt.getText();

     jl.setText(inoutt); 
     }
     });

Why dose this lower section have the problem "Exception in thread "AWT-EventQueue-0" java.lang.StringIndexOutOfBoundsException: String index out of range:(how ever many characters i entered)".str is receiving what is typed in the Jtextfield and im trying to filter the input to give a different output. With out a filter it works fine like above just press enter,but when i try to press the button i and filter i get an error.

//button
     jp.add(jb);
     jb.addActionListener(new ActionListener()
     {
     public void actionPerformed(ActionEvent e)
     {
     String str = jt.getText();
     String text="";
     int A=0;
     int B=1;
     int C=2;
     for(int num=0;num<=str.length()/3;num++)
        {
            if (str.charAt(A) == 'T'&&str.charAt(B) == 'A'&&str.charAt(C)=='S')
            {
            text+="smell tasty";
            }
            else if(str.charAt(A) == 'B'&&str.charAt(B) == 'A'&&str.charAt(C)=='N')
            {
            text+="bannanas";
            }
            A+=3;
            B+=3;
            C+=3;
        }
     jl.setText(text);
     }
     });
     jp.add(jl);
     window.add(jp);
    }
}

Answer 1

your index is overshooting use this instead

for(int num=0;num<str.length()/3;num++)

just < not <=

Answer 2

The problem seems to the fact that you are overthinking the it. Remember, Java String s are zero indexed so num<=str.length()/3 should be something more like num < str.length()/3

But, having said that, the whole thing seems woefully inefficient (not to mention confusing)

You could use something like...

for (int num = 0; num + 3 < str.length(); num++) {
    String test = str.substring(num, 3);
    if ("tas".equalsIgnoreCase(test)) {
        text = "smell tasty";
        break;
    } else if ("ban".equalsIgnoreCase(test)) {
        text = "bannanas";
        break;
    }
}

But even that's a long way around an otherwise simple problem.

Instead, you could simply use something like...

String str = "tas";
String text = "";
if (str.toLowerCase().contains("tas")) {
  text = "smell tasty";
} else if (str.toLowerCase().contains("ban")) {
  text = "bannanas";
}