swing中通过按钮打开文件实例

package test;

import java.awt.*;
import java.io.*;
import java.awt.event.*;

public class wenjian
    extends Frame
    implements ActionListener {
  FileDialog open = new FileDialog(this, "打开文件",
                                   FileDialog.LOAD);
  String fileName;
  Button b_dakai = new Button("打开");
  TextArea text = new TextArea();
  wenjian() {
    super("文件的打开");
    setBounds(400, 200, 400, 300);
    b_dakai.addActionListener(this);
    add(text);
    add(b_dakai, "South");
    setVisible(true);
  }

  public void actionPerformed(ActionEvent e) {
    if (e.getSource() == b_dakai) {
      open.show();
      fileName = open.getDirectory() + open.getFile();
      if (fileName != null) {
        readFile(fileName);
      }
    }
  }
//这是一个打开文件文件的方法
  public void readFile(String fileName) {
    try {
      File file = new File(fileName);
      FileReader readIn = new FileReader(file);
      int size = (int) file.length();
      int charsRead = 0;
      char[] content = new char[size];
      while (readIn.ready()) {
        charsRead += readIn.read(content, charsRead, size - charsRead);
      }
      readIn.close();
      text.setText(new String(content, 0, charsRead));
    }
    catch (IOException e) {
      System.out.println("Error Opening file");
    }
  }

  public static void main(String args[]) {
    new wenjian().addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        System.exit(0);
      };
    });
;
  }
}