JscrollBar não aparece

public class Sheet extends JPanel {

private JScrollPane scroll;

private JLabel labelOrigem = new JLabel(“Colunas de Origem”);

private JLabel labelDestino = new JLabel(“Colunas de Destino”);

private JSeparator separator = new JSeparator(SwingConstants.VERTICAL);

private JTextField sheeetNumField = new JTextField();

private JTextField[][] colunasArr = new JTextField[30][2];
private JTextField textFieldA, textFieldB;

private final int PONTO_A = 150;
private final int PONTO_B = 345;
private int alturaCampo = 40;

private int numSheet;
private String[][] colunasStrArr = new String[15][2];

public Sheet(){
	
	this.setLayout(null);
		
	Border pathNumSheet = BorderFactory.createTitledBorder("Index");
	Font font = new Font("Courier", Font.BOLD,20);
	sheeetNumField.setBorder(pathNumSheet);
	sheeetNumField.setBackground(new Color(238,238,238));
	sheeetNumField.setFont(font);
	
	adiciona(sheeetNumField, 10, 10, 50, 50);
	
	adiciona(labelOrigem, 100, 0, 150, 50);
	adiciona(labelDestino, 300, 0, 150, 50);
	adiciona(separator, 250, 20, 1, 320);
	
	for(int i=0; i<30; i++){
		textFieldA = new JTextField();
		textFieldB = new JTextField();
		
		adiciona(textFieldA, PONTO_A, alturaCampo, 20, 20);
		adiciona(textFieldB, PONTO_B, alturaCampo, 20, 20);
		
		colunasArr[i][0]= textFieldA;
		colunasArr[i][1]= textFieldB;
		
		alturaCampo = alturaCampo+20;
	}
	scroll = new JScrollPane();
	scroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
	scroll.setViewportView(this);
}
 private  void adiciona( Component Componente , int nColuna , int nLinha , int nLargura , int nAltura ) {
        this.add( Componente ) ;                      
        Componente.setBounds( nColuna , nLinha , nLargura , nAltura );
    }