利用一些元件編寫一個java登入介面：

import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField; 
public class Tsar {
    public static void main(String[] args) {
    	JFrame frame = new JFrame("JAVA 課堂登入系統");
    	frame.setSize(350,200);
    	frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel panel = new JPanel();
        frame.add(panel);
        panel.setBackground(Color.white );
          frame.setVisible(true);
          JButton bl = new JButton("點選進入java課堂");
          bl.setBounds(30,50,165,50);
          panel.add(bl);
          bl.addActionListener(new ActionListener(){
        	  public void actionPerformed(ActionEvent e){
        		  JFrame frame2 = new JFrame("登入介面");
        		  frame2.setSize(300, 150);
        	    	JPanel panel2 = new JPanel();
        	    	frame2.add(panel2);
        	    	//placeComponents(panel2);
        		panel.setBackground(Color.black );
        		panel.setLayout(null);
        		JLabel userLabel = new JLabel("學號：");
        		userLabel.setBounds(10,20,80,25);
        		panel2.add(userLabel);
        		JTextField userText = new JTextField(20);
        		userText.setBounds(100,20,165,25);
        		panel2.add(userText);
        		JLabel passwordLabel = new JLabel("密碼：");
        		panel2.add(passwordLabel);
        		passwordLabel.setBounds(10,50,80,25);
        		JPasswordField passwordText = new JPasswordField(20);
        	    passwordText.setBounds(100,50,165,25);
        		panel2.add(passwordText);		
        		JButton loginButton = new JButton("一起來學習java吧");
        		loginButton.setBounds(10,80,165,25);
        		panel2.add(loginButton);
        		//panel2.add(bl);
        		frame2.setVisible(true);
        	  }
          });
    }
}