filedemo2.java

这也是一个JAVA入门学习的一个简单的程序

//FileDemo2.java
import java.io.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class FileDemo2 extends JFrame implements  ActionListener
{
	private JTextArea inputTextArea;   //文件内容显示区域
	private JButton openButton;        //打开按钮
	private JLabel label;              //提示用户打开文件
	private FileInputStream inFile;     //输入文件流 
	private File file;
	byte[] bufferArray=new byte[4096];
	public FileDemo2()
	{
		Container container=getContentPane();
		container.setLayout(new FlowLayout());
		label=new JLabel("The file test.txt content:");
		label.setForeground(Color.red);
		container.add(label,BorderLayout.NORTH);
		inputTextArea=new JTextArea("",10,20);
		inputTextArea.setEditable(false);
		container.add(new JScrollPane(inputTextArea),BorderLayout.CENTER);
		openButton=new JButton("open");
		container.add(openButton,BorderLayout.SOUTH);
		openButton.addActionListener(this);
		setSize(300,300);
		setVisible(true);
	}
	//时间处理
	public void actionPerformed(ActionEvent event)
	{
		if(event.getSource()==openButton)
		{
			try
			{
				file=new File("test.txt");
				int fileLength=(int)file.length();
				inFile=new FileInputStream(file);
				//将用户写入的信息保存到文件
				inFile.read(bufferArray,0,fileLength);
				String str=new String();
				for(int i=0;i<fileLength;i++)
				{
					str+=(char)bufferArray[i];
				}
				inputTextArea.setText(str);
				inFile.close();
				//提示操作成功
				JOptionPane.showMessageDialog(this,"The file test.txt has been opened!");
			}
			catch(IOException e)
			{
				//发生异常时给出提示信息
				JOptionPane.showMessageDialog(this,"Error when openning file or closing the file!","Error",JOptionPane.ERROR_MESSAGE);
				System.exit(1);//退出
			}
		}
	}
	public static void main(String [] args)
	{
		FileDemo2 fileDemo2=new FileDemo2();
		fileDemo2.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	}
}