my teacher wants the tictactoe game to have a button called play that resets the tictactoe game my button doesn't work....what did i do wrong?

//TicTacToePanel.java Author Carien Anderson
//Represents tic tac toe game board and allows peer to peer competition

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.JOptionPane;
import java.io.*;

public class TicTacToePanel extends JPanel
{
	//instance data
	private JButton tile[][] = new JButton[3][3], exit, play;
	private String xoro = " ";
	private boolean win = false;
	private int count =0;
	private JPanel panel;
	private ButtonListener listener;
	
	public TicTacToePanel()
	{
			//panel for gameboard
		   panel = new JPanel();
			
			panel.setPreferredSize(new Dimension(280,275));
			panel.setLayout(new GridLayout(3,3));
			
		   listener = new ButtonListener();
			
			//create and add button to panel and add the button listener
		
			for(int i=0; i<3; i++)
			{
				for(int j=0; j<3; j++)
				{
					tile[i][j] = new JButton();
					panel.add(tile[i][j]);
					tile[i][j].addActionListener(listener);
				}
			}
			
			exit = new JButton ("EXIT");
			exit.addActionListener(listener);
			
			play = new JButton("Play Again");
			play.addActionListener(listener);
			
			this.add(panel, BorderLayout.CENTER);
			this.add(exit, BorderLayout.SOUTH);
			this.add(play, BorderLayout.SOUTH);
	}
	
			
	private class ButtonListener implements ActionListener
	{
		public void actionPerformed (ActionEvent click)
		{	
			JButton place = (JButton)click.getSource();
			
			if(place == exit)
				System.exit(0);
				
			if(place == play)
				pAgain(panel);
				
			else		
			{
				//determines whether player is x or o by using modulo division
				
					count++;
				
					if(count % 2 == 0)
					{
						xoro = "O";
					}
					
					else
					{
						xoro = "X";
					} 
				 
				 //determines if place is filled and alerts player or sets x or o
				 if(place.getText() == " ")
				 { 
				 	count--;
					
					JOptionPane.showMessageDialog(null, "Place is already taken");
				 }
				 
				 else	
				 {
				 	 place.setText(xoro);
					 place.setEnabled(false);
				 }
				 
				 
				//determines winner
				for(int i=0; i<3; i++)
				{
					if(tile[i][0].getText()=="X" && tile[i][1].getText()=="X" && tile[i][2].getText()=="X")
						win = true;
					else if(tile[i][0].getText()=="O" && tile[i][1].getText()=="O" && tile[i][2].getText()=="O")
						win = true;
					else if(tile[0][i].getText()=="X" && tile[1][i].getText()=="X" && tile[2][i].getText()=="X")
						win = true;
					else if(tile[0][i].getText()=="O" && tile[1][i].getText()=="O" && tile[2][i].getText()=="O")
						win = true;
					else if(tile[0][0].getText()=="X" && tile[1][1].getText()=="X" && tile[2][2].getText()=="X")
						win = true;
					else if(tile[0][2].getText()=="O" && tile[1][1].getText()=="O" && tile[2][0].getText()=="O")
						win = true;

				}
			
				if(win == true)
				{
					JOptionPane.showMessageDialog(null, xoro + " wins the game!");
				}
			  
			   else if(count == 9 && win == false)
				{
					JOptionPane.showMessageDialog(null, "The game was tie!");
										
				}
			}
		}
	}
	
	public void pAgain(JPanel panel)
	{
			panel= null;
				
			panel.setPreferredSize(new Dimension(280,275));
			panel.setLayout(new GridLayout(3,3));
			
		   listener = new ButtonListener();

			
			for(int i=0; i<3; i++)
			{
				for(int j=0; j<3; j++)
				{	
					tile[i][j] = new JButton();
					tile[i][j].setText(" ");
					panel.add(tile[i][j]);
					tile[i][j].addActionListener(listener);
				}
			}
			
			this.add(panel, BorderLayout.CENTER);
	}
}

You set panel to null and then you are trying to use it. Maybe after the null you need to create a new one.

Also use equals method to compare Strings:

if (place.getText().equals(" ")) {

}
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