This is a school project. I need to read jokes from multiple files and show them in separate threads. It complies but I keep getting IndexOutOfBoundsExceptions. Any tips or help you can give would be greatly appreciated.

import javax.swing.*;
import java.awt.*;
import java.io.File;
import java.io.*;
import java.io.FileNotFoundException;
import java.awt.event.*;
import java.util.*;


public class JokeOutput{
	public static void main (String args[])
	{
		while(true)
		{
		String tempString = (String)JOptionPane.showInputDialog("Enter File Name");
		Thread temp = new Thread(new FileWatcher(tempString));
		temp.run();
		}
	}
}
class FileWatcher extends Thread{
	private String fileName;
	private File tempfile;
	public FileWatcher(String s){
		fileName = s;
		tempfile = new File(fileName);
	}
	public void run(){
		try{
		System.out.println("Checking for file \"" + fileName + "\"");
		while(!tempfile.exists()){
			System.out.println("File \"" + fileName + "\" not found");
			this.sleep(10000);
		}
		System.out.println("File \"" + fileName + "\" found");
		if(fileName.substring((fileName.length() - 3)).equals("obj"))
		{
			 Thread newThread = new FileWatcherObj(tempfile);
			 newThread.run();
		}
		if(fileName.substring((fileName.length() - 3)).equals("txt"))
		{
			 Thread newThread = new FileWatcherTxt(tempfile);
			 newThread.run();

		}
		if(fileName.substring((fileName.length() - 3)).equals("dat"))
		{
			 Thread newThread = new FileWatcherDat(tempfile);
			 newThread.run();
		}

	}catch(InterruptedException e){}
	}
}
class FileWatcherObj extends Thread{
	private ObjectInputStream in;
	private ArrayList<Joke> jokeList = new ArrayList(10);
	private JokeFrame frame;
	public FileWatcherObj(File f){
		try{
		in = new ObjectInputStream(new FileInputStream(f));
		frame = new JokeFrame();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
        for(int i = 0; i < 10; i++)
		{
			Joke tempJoke = new Joke();
			tempJoke = (Joke)in.readObject();
			jokeList.add(tempJoke);
		}
	}catch(FileNotFoundException e){}catch(IOException g){}catch(ClassNotFoundException e){}
	}
	public void run(){
		try{

		while(true)
		{
			int random = (int)((Math.random() * jokeList.size())+1);
			frame.showJoke(jokeList.get(1).toString());
			this.sleep(10000);
		}
	}catch(InterruptedException f){}
	}
}
class FileWatcherDat extends Thread{
	private DataInputStream in;
	private ArrayList<Joke> jokeList = new ArrayList(10);
	private JokeFrame frame;
	public FileWatcherDat(File f){
		try{
		in = new DataInputStream(new FileInputStream(f));
		frame = new JokeFrame();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
        for(int i = 0; i < 10; i++)
		{
			Joke tempJoke = new Joke(in.readLine());
			jokeList.add(tempJoke);
		}
	}catch(FileNotFoundException e){}catch(IOException g){}
	}
	public void run(){
		try{

		while(true)
		{
			int random = (int)((Math.random() * jokeList.size())+1);
			frame.showJoke(jokeList.get(random).toString());
			this.sleep(10000);
		}
	}catch(InterruptedException f){}
	}
}
class FileWatcherTxt extends Thread{
	private BufferedReader in;
	private ArrayList<Joke> jokeList = new ArrayList(10);
	private JokeFrame frame;
	public FileWatcherTxt(File f){
		try{
		in = new BufferedReader(new FileReader(f));

		frame = new JokeFrame();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
        for(int i = 0; i < 10; i++)
		{
			Joke tempJoke = new Joke(in.readLine());
			jokeList.add(tempJoke);
		}
	}catch(FileNotFoundException e){}catch(IOException g){}
	}
	public void run(){
		try{

		while(true)
		{
			int random = (int)((Math.random() * jokeList.size())+1);
			frame.showJoke(jokeList.get(random).toString());
			this.sleep(10000);
		}
	}catch(InterruptedException f){}
	}
}
class Joke implements Serializable{
	private String joke;
	public Joke(){}
	public Joke(String j){
		joke = j;
	}
	public String toString(){
		return joke;
	}
}
class JokeFrame extends JFrame{
	private JTextArea text = new JTextArea();
	public JokeFrame(){
		this.setTitle("Jokes");
        this.setSize(600, 400);
		this.add(text);
		text.setVisible(true);
	}
	public void showJoke(String s)
	{
		text.append(s);
	}
}

jokeList.get is giving this problem...
you arraylist is not populated and when you are trying to get it from selected index it is throwing this exception

jokeList.get is giving this problem...
you arraylist is not populated and when you are trying to get it from selected index it is throwing this exception

I tried to populate the arraylist with the code

#
for(int i = 0; i < 10; i++)
#
{
#
Joke tempJoke = new Joke();
#
tempJoke = (Joke)in.readObject();
#
jokeList.add(tempJoke);
#
}

Do you know why this isn't working?

Joke tempJoke = new Joke();
tempJoke = (Joke)in.readObject();
jokeList.add(tempJoke);
----------------------------------
might be tempjoke is coming null
chk the nullpointer

Joke tempJoke = new Joke();
tempJoke = (Joke)in.readObject();
if(tempJoke !=null)
jokeList.add(tempJoke);

and after adding chk ths size of your arraylist

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