20170204Exception in thread "main" java.lang.NullPointerException

Exception in thread "main" java.lang.NullPointerException  at com.txw.Ftest.getControlPanel(Ftest.java:28)  at com.txw.Ftest.getJContentPane(Ftest.java:93)  at com.txw.Ftest.initialize(Ftest.java:85)  at com.txw.Ftest.(Ftest.java:81)  at com.txw.Ftest.main(Ftest.java:99)

public class Ftest extends JFrame {
	private JScrollPane scrollPane;
	private static final long serialVersionUID=1L;
	private JPanel jContentPane=null;
	private JTextArea jTextArea=null;
	private JPanel controlPanel=null;
	private JButton openButton=null;
	private JButton closeButton=null;
	
	private JTextArea getJTextArea(){
		if(jTextArea==null){
			jTextArea=new JTextArea();
		}
		return jTextArea;
	}
	private JPanel getControlPanel(){
		if(controlPanel==null){
			FlowLayout flowLayout=new FlowLayout();
			flowLayout.setVgap(1);
			controlPanel=new JPanel(); //缺少此行就会报错
			controlPanel.setLayout(flowLayout);
			controlPanel.add(getOpenButton(), null);
			controlPanel.add(getCloseButton(),null);
		}
		return controlPanel;
	}
	private JButton getOpenButton(){
		if(openButton==null){
			openButton=new JButton();
			openButton.setText("写入文件");
			openButton
			//.addActionListener(new java.awt.event.ActionListerner(){
				//java.awt.event.ActionListerner cannot be resolved to a type, "ActionListerner"字母写错，改为“ActionListener”
				.addActionListener(new java.awt.event.ActionListener(){
				public void actionPerformed(ActionEvent e){
					File file=new File("word.txt");
					try{
						FileWriter out=new FileWriter(file);
						String s=jTextArea.getText();
						out.write(s);
						out.close();
					}catch(Exception e1){
						e1.printStackTrace();
					}
				}
			});
		}
		return openButton;
	}
	private JButton getCloseButton(){
		if(closeButton==null){
			closeButton=new JButton();
			closeButton.setText("读取文件");
			closeButton
			.addActionListener(new java.awt.event.ActionListener(){
				public void actionPerformed(ActionEvent e){
					File file=new File("word.txt");
					try{
						FileReader in=new FileReader(file);
						char byt[]=new char[1024];
						int len=in.read(byt);
						jTextArea.setText(new String(byt,0,len));
						in.close();
					}catch(Exception e1){
						e1.printStackTrace();
					}
				}
			});
		}
		return closeButton;
	}
	public Ftest(){
		super();
		initialize();
	}
    private void initialize(){
    	this.setSize(300,200);
    	this.setContentPane(getJContentPane());
    	this.setTitle("JFrame");
    }
    private JPanel getJContentPane(){
    	if(jContentPane==null){
    		jContentPane=new JPanel();
    		jContentPane.setLayout(new BorderLayout());
    		jContentPane.add(getScrollPane(), BorderLayout.CENTER);
    		jContentPane.add(getControlPanel(),BorderLayout.SOUTH);
    	}
    	return jContentPane;
    }
	public static void main(String[] args) {
		// TODO Auto-generated method stub
    Ftest thisClass=new Ftest();
    thisClass.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    thisClass.setVisible(true);
	}
	protected JScrollPane getScrollPane(){
		if(scrollPane==null){
			scrollPane=new JScrollPane();
			scrollPane.setViewportView(getJTextArea());
		}
		return scrollPane;
	}

}