my program cant read the keys because of "Exception in thread "AWT-EventQueue-0" java.lang.UnsupportedOperationException: Not supported yet."

Question

I am programming a snake game on Netbeans Java 8 and when I programmed the keys part, it didn't work because of Exception in thread "AWT-EventQueue-0" java.lang.UnsupportedOperationException: Not supported yet .

Can anyone tell me whats the solution or any other method I can use to control my snake specially in line 135 .

**package mainclass;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.ArrayList;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JPanel;

/**
 *

 */
public class gamepanel extends JPanel implements Runnable,KeyListener{


       private static final long serialversionid = 1L;

    public static final int WIDTH =500,HEIGHT =500;

    private Thread thread;

    private boolean  running;
    private boolean right =true,left=false,up=false,down=false;
    private bodyparts b;
    private ArrayList<bodyparts> snake;
    private int xcoor = 10,ycoor = 10, size= 5;
    private int ticks =0;


public gamepanel(){

    setFocusable(true);
    setPreferredSize(new Dimension(WIDTH,HEIGHT));
    addKeyListener(this);
    snake = new ArrayList<bodyparts>();
    start();


}
  public void start(){

           running = true;
           thread = new Thread(this);
           thread.start();
  }  
  public void stop(){

           try {
               running = false;
               thread.join();
           } catch (InterruptedException ex) {
               Logger.getLogger(gamepanel.class.getName()).log(Level.SEVERE, null, ex);
           }



  } 
  public void tick(){
      if (snake.size() == 0) {
          b = new bodyparts(xcoor,ycoor,10);
          snake.add(b);
      }
      ticks++;
      if(ticks>250000){
      if(right)xcoor++;
      if(left)xcoor--;
      if(up)ycoor--;
      if(down)ycoor++;
      ticks = 0;
      b = new bodyparts(xcoor,ycoor,10);
      snake. add (b);
      if(snake.size()>size){
          snake.remove(0);
          if(snake.size()>size){

          snake.remove(0);
          }
      }





  }
  }
  public void paint(Graphics g){
      g.setColor(Color.black);
      g.fillRect(0, 0, WIDTH, HEIGHT);



      for (int i = 0; i < WIDTH/10; i++) {
         g.drawLine(i*10, 0, i*10, HEIGHT);


      }
   for (int i = 0; i < WIDTH/10; i++) {
         g.drawLine(0,i*10, HEIGHT, i*10);


      }
      for (int i = 0; i < snake.size(); i++) {
          snake.get(i).draw (g);

      }

  }
  public void run(){
while (running){
repaint();
    tick();


}







}



   // @Override
    public void keyPressed(KeyEvent e) {

int key = e.getKeyCode();
if(key==KeyEvent.VK_RIGHT&&!left){
right = true;
left=false;
up= false;
down = false;

}
if(key==KeyEvent.VK_LEFT&&!right){
right = false;
left=true;
up= false;
down = false;

}
if(key==KeyEvent.VK_UP&&!down){
right = false;
left=false;
up= true;
down = false;

}
if(key==KeyEvent.VK_DOWN&&!up){
right = false;
left=false;
up= false;
down = true;

}
    }

   // @Override
    public void keyReleased(KeyEvent e) {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
     //@Override
    public void keyTyped(KeyEvent e) {


}

    }**

I expect the snake to be controlled, but its not and when I am trying to control it the is a big exception Exception in thread "AWT-EventQueue-0" java.lang.UnsupportedOperationException: Not supported yet.

Answer 1

@SizeableShrimp has identified the cause of your exception.

When you implement KeyListener in an application class you need to provide implementations for the keyPressed and keyReleased method. Apparently, you did this using an IDE to generate stub implementations.

The problem is that the stub implementations won't necessarily work . The IDE doesn't "know" what the methods mean ... or what they should actually do in your application. In this case, the IDE has inserted an implementation that is designed to throw an exception if it is called ... reminding you that you need to look at the code and implement the method properly.

---

In this case, it is really necessary to implement the keyRelease method properly because it will be called whenever you release a key that you previously pressed.

But the implementation is straightforward. Really straightforward. Your method doesn't to do anything at all, because key releases are not relevant to your game.

OR BETTER STILL : Do this a different way as per @MadProgrammer's comments!

---

Lessons:

1. It is a good idea to read the javadocs for the interfaces that you add to your classes, so that you understand what needs to be implemented.
2. Read the code that the IDE completion wizards add for you. They don't always get it right. (They can't!)
3. When you get an exception, read the stacktrace. It will tell you where the exception occurred. Then look at the code ... and think about it.
4. The message "Not supported yet." is a big clue. It is saying that someone hasn't finished the job of coding something. (In this case, the someone was you.)

A programmers most important debugging tool is his/her brain, and the ability to put the clues together to diagnose problems. It takes practice. My advice would be to start practicing!

Answer 2

public void keyReleased(KeyEvent e) {
    throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
}

This method is causing the problem. Remove the line where it throws the exception and leave it empty. The instant you let go of a key this method is run and throws the exception.