本实例创建Swing窗体，单击窗体中的“写入文件”按钮实现写入功能，单击“读取文件”按

本实例创建Swing窗体，单击窗体中的“写入文件”按钮实现写入功能，单击“读取文件”按钮实现从文件中读取信息显示在文本框中

package Zhang15;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.io.File;

import java.io.FileReader;

import java.io.FileWriter;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JPanel;

import javax.swing.JTextArea;

import javax.swing.SwingConstants;

import javax.swing.WindowConstants;

import java.awt.event.*;

import java.io.*;

import java.awt.*;

public class Ftest extends JFrame{

    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;

    public void CreateJFrame(String title) {

JFrame jf = new JFrame(title);

Container container = jf.getContentPane();

JLabel jl = new JLabel("这是一个JFrame窗体");

jl.setHorizontalAlignment(SwingConstants.CENTER);

container.add(jl);

container.setBackground(Color.white);

jf.setVisible(true);

jf.setSize(200, 150);

jf.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

}

private JButton getOpenButton() {

if(openButton==null) {

openButton = new JButton();

openButton.setText("写入文件");

openButton.addActionListener(new 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 getClosrButton() {

if(closeButton==null) {

closeButton = new JButton();

    closeButton.setText("读取文件");

    closeButton.addActionListener(new 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(getContentPane());

this.setTitle("JFrame");

}

private JPanel getJContentPane() {

if(jContentPane==null) {

jContentPane = new JPanel();

jContentPane.setLayout(new BorderLayout());

jContentPane.add(getClosrButton(),Borderalayout.CENTER);

jContentPane.add(JFrame(),BorderLayout.SOUTH);

}

return jContentPane;

}

public static void main(String[] args) {

Ftest thisClass new Ftest();

thisClass.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

thisClass.setVisible(true);

}

}

为什么是空白