Manipulando JavaSwing

public Jogo(){
    	this.setTitle("Advinhe o número.");
    	this.setSize(350,260);
    	
    	//Define o numero aleatorio a ser acertado
    	this.definirNumAleatorio();
    	
		list.setVisibleRowCount(5);
		
		list.setSize(100,100);
		
		// não permite múltiplas seleções
		list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
		list.setListData(listData.toArray());
		
    	buscar.addActionListener(new TratamentoEventoBotao());
    	novo.addActionListener(new TratamentoEventoBotao());
    	
    	addItens();
    }
    
    private void addItens(){
    	
    	Container tbpanel = this.getContentPane();
    	tbpanel.setLayout(new FlowLayout(FlowLayout.LEFT));
    	
    	tbpanel.add(new JLabel("Tenho um número no intervalo de 0-1000"));
    	tbpanel.add(new JLabel("Que Número Tenho?"));
    	tbpanel.add(new JLabel("                                                      "));
    	tbpanel.add(label_result);
    	tbpanel.add(numero);
    	tbpanel.add(new JLabel("                                                      "));
    	tbpanel.add(buscar);
    	tbpanel.add(novo);
    	tbpanel.add(new JLabel("                                                      "));
    	tbpanel.add(new JLabel("Numero de tentativas -"));
    	tbpanel.add(cont);
    	tbpanel.add(new JLabel("                                                      "));
    	tbpanel.add( new JScrollPane( list ) );
    	this.setContentPane(tbpanel);
    

    	this.setVisible(true);
    }