Problema com JButton

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.BorderFactory;
import javax.swing.JOptionPane;
import javax.swing.JMenuBar;
import javax.swing.JMenu;
import javax.swing.JMenuItem;
import java.awt.GridLayout;
import java.awt.Color;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.lang.String;

public class Sudoku	extends	JFrame implements ActionListener{
	/*Declaração de	atributos da classe*/
	private	JButton	[][] botao = new JButton[9][9];
	private	int	[] novo	= new int[100];
//	private	int	[] novo_aux	= new int[15];
	private	JFrame win = new JFrame("Sudoku");
	private	JPanel [] painel = new JPanel[9];
	
	private	JMenuBar barra = new JMenuBar();
	private	JMenu menu1	= new JMenu("Opçoes");
	private	JMenuItem item1	= new JMenuItem("Novo Jogo");
	private	JMenuItem item2	= new JMenuItem("Sobre...");
	private	JMenuItem item3	= new JMenuItem("Sair");
	/*Construtor da	Classe ele faz os botoes e a janela*/		
	public Sudoku(){
		fazBotao();
		fazJanela();
		novoJogo();
		limpa_matriz();
	}
	/*Metodo que faz o meno	da Barra de	Menu*/
	public JMenuBar	menu(){
		item1.addActionListener(this);
		menu1.add(item1);
		item2.addActionListener(this);
		menu1.add(item2);
		item3.addActionListener(this);
		menu1.add(item3);
		barra.add(menu1);
		return barra;
	}
	/*Metodo que faz os	botoes*/
	public void	fazBotao(){
		for(int	i =	0; i < botao.length; i++){
			painel[i] =	new	JPanel(new GridLayout(3,3));
			painel[i].setBorder(BorderFactory.createLineBorder(Color.BLACK,	1));
			for(int	j =	0; j < botao.length; j++){
				botao[i][j]	= new JButton();
				botao[i][j].setText(" ");
				botao[i][j].addActionListener(this);
			painel[i].add(botao[i][j]);
			}
		}
	}
	/*Metodo que faz as	janelas*/
	public void	fazJanela(){
		win.setJMenuBar(menu());
		win.getContentPane().setLayout(new GridLayout(3,3));
		win.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
		for(int	i =	0; i < painel.length; i++){ 
			win.getContentPane().add(painel[i]);
		}
		//win.pack();
		win.setSize(390,350);
		win.setDefaultLookAndFeelDecorated(false);
		win.setResizable(false);
		win.setVisible(true);   
	}
	


	public void	limpa_matriz(){
	int loop = 0;
		while( loop < 10){
			for(int	line = 0; line < botao.length; line++){
				for(int	coln = 0; coln < botao.length; coln++){
					for(int	line1 =	0; line1 < botao.length; line1++){
						for(int	coln1 =	0; coln1 < botao.length; coln1++){
							if(!(botao[line][coln].getText().equals(" "))){
								if(!(botao[line1][coln1].getText().equals("	"))){
									String x = (botao[line][coln].getName());
									String y = (botao[line1][coln1].getName());
									if( x.equals(y)){
										botao[line][coln].setText("	");
									}								
								}		
							}   
						}
					}
				}
			}
		loop = loop + 1;
		}
	}
	
	
	/*Metodo que inicia	um novo	Jogo*/
	
	public void	novoJogo(){
		int	lin, col;
		boolean	val;
		
		for(int	i =	0; i < novo.length;	i++){
			
			novo[i]	= (int)	(1 + (Math.random()	* 9)); 
		//	novo_aux[i]	= (int)(numero);
		}
		
		for(int	i =	0; i < botao.length; i++){
			for(int	j =	0; j < botao.length; j++){
				botao[i][j].setText(" ");
			}
		}
		
		for(int	i =	0; i < novo.length;	i++){
			lin	= (int)	(Math.random() * 9);
			col	= (int)	(Math.random() * 9);

			for(int	coluna = 0;	coluna < botao.length; coluna++){
				if (!(botao[lin][coluna].getText().equals("	"))	&& botao[lin][coluna].getText().compareTo(Integer.toString(novo[i])) ==	0 ){
					novo[i]	= 99;
				}				
			}

			for(int	linha =	0; linha < botao.length; linha++){
				if (!(botao[linha][col].getText().equals(" ")) && botao[linha][col].getText().compareTo(Integer.toString(novo[i])) == 0 ){
					novo[i]	= 99;
				}				
			}
			
			if (novo[i]	!= 99){
				botao[lin][col].setText(String.valueOf(novo[i]));
			}
		}

		limpa_matriz();

	}			
	/*Metodo que gerencia os Eventos da	Classe*/
	public void	actionPerformed(ActionEvent	e){
		String n = " ";
		int	nro;
		
		/*No menu Novo Jogo*/
		if(e.getSource() ==	item1){
			novoJogo();
			limpa_matriz();
		}
		/*No menu Sobre...*/
		if(e.getSource() ==	item2){
			JOptionPane.showMessageDialog(null,	"Sudoku!!! \n" +
												"Inteligência Artificial I \n" +
												"Desenvolvedor:" +
												"\nAlker Barni RA. 986956","Sobre Sudoku", JOptionPane.WARNING_MESSAGE);
		}
		/*No menu Sair*/
		if(e.getSource() ==	item3){
			System.exit(0);
		}
		/*Aqui eu vou gerenciar	os eventos de cada botao do	Array*/
		for(int	i =	0; i < botao.length; i++){
			for(int	j =	0; j < botao.length; j++){
				if(e.getSource() ==	botao[i][j]){
					do{	/*loop de integridade de dado*/
						nro	= Integer.parseInt(JOptionPane.showInputDialog(null, "Digite o numero",	"Sudoku", JOptionPane.WARNING_MESSAGE));
						if(nro <= 0	|| nro > 9){
							JOptionPane.showMessageDialog(null,	"Numero	Inválido", "Sudoku Notifica", JOptionPane.WARNING_MESSAGE);
						}
					}while(nro <= 0	|| nro > 9);/*Fim do loop*/
					n =	n.valueOf(nro);
					botao[i][j].setText(n);
					if(e.getSource() ==	botao[i][j]){
						break;
					}
				}
			}
		}
		/*Fim dos Eventos*/
		
	}
	/*Metodo Principal Chamando	o Construtor*/
	public static void main(String args[]){
		new	Sudoku();
	}
}

public void	limpa_matriz(){
	int loop = 0;
		while( loop < 10){
			for(int	line = 0; line < botao.length; line++){
				for(int	coln = 0; coln < botao.length; coln++){
					for(int	line1 =	0; line1 < botao.length; line1++){
						for(int	coln1 =	0; coln1 < botao.length; coln1++){
							if(!(botao[line][coln].getText().equals(" "))){
								if(!(botao[line1][coln1].getText().equals("	"))){
									String x = (botao[line][coln].getName());
									String y = (botao[line1][coln1].getName());

                                                   // o "x" esta vindo null!

									if( x != null && x.equals(y)){
										botao[line][coln].setText("	");
									}
								}
							}
						}
					}
				}
			}
		loop = loop + 1;
		}
	}