login.java

java课程的资料以及实验的代码

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.io.*;//导入io包

public class Login extends JFrame implements ActionListener
{
	JPanel p;
	JLabel lblCustName;
	JLabel lblPwd;	
	JLabel lblMsg;
	
	JTextField txtCustName;
	JPasswordField txtPwd;
	
	JButton btnLogin;
	
	//
	public Login()
		{
		p = new JPanel();
		
		Container c = new Container();
		c = this.getContentPane();
		
		GridBagLayout gb = new GridBagLayout();
		GridBagConstraints gbc = new GridBagConstraints();
		
		p.setLayout(gb);
		
		lblCustName	= new JLabel("登 录 名：");
		txtCustName = new JTextField(10);
		
		lblPwd	= new JLabel("登录密码：");
		txtPwd = new JPasswordField(10);
		
		btnLogin = new JButton("确 定");
		lblMsg	= new JLabel(" ");
		
		//
		gbc.gridx = 0;
		gbc.gridy = 0;
		gb.setConstraints(lblCustName,gbc);
		p.add(lblCustName);
		
		gbc.gridx = 1;
		gbc.gridy = 0;
		gb.setConstraints(txtCustName,gbc);
		p.add(txtCustName);
		//
		gbc.gridx = 0;
		gbc.gridy = 1;
		gb.setConstraints(lblPwd,gbc);
		p.add(lblPwd);
		
		gbc.gridx = 1;
		gbc.gridy = 1;
		gb.setConstraints(txtPwd,gbc);		
		p.add(txtPwd);
		
		gbc.gridx = 0;
		gbc.gridy = 2;
		gb.setConstraints(btnLogin,gbc);		
		p.add(btnLogin);
		
		gbc.gridx = 1;
		gbc.gridy = 2;
		gb.setConstraints(lblMsg,gbc);		
		p.add(lblMsg);		
		c.add(p);
		
		//注册监听器
		btnLogin.addActionListener(this);
		this.setSize(300,200);
		this.show();
	}
	
	public void actionPerformed(ActionEvent e)
	{
		try
		{
			if(e.getSource()==btnLogin)
			{
				writeFile();
			}
		}
		catch(Exception ee)
		{
			lblMsg.setText(ee.getMessage());	
		}
	
	}
	
	//writeFile()方法写入文件
	public void writeFile()
	{
		String custInfo = txtCustName.getText() +":" + new String(txtPwd.getPassword());
		try
		{
			RandomAccessFile logFile = new RandomAccessFile("e:\\cust1.txt","rw");
			long lg = logFile.length();
			logFile.seek(lg);//文件指针定位
			if(lg==0)
				logFile.writeBytes(custInfo);
			else
				logFile.writeBytes("\t" + custInfo);

			lblMsg.setText("用户信息已写入文件");	
		}

		catch(IOException ioe)
		{
		   JOptionPane.showMessageDialog(null,"无法写入文件："+ioe.getMessage());			
		}
		
	}
	public static void main(String a[])
	{
		new Login();
	}
}