验证码

package yzm;
	import java.util.Random;
	import java.awt.Container;
	import java.awt.Dimension;
	import java.awt.FlowLayout;

	import javax.swing.ImageIcon;//顶级容器即空白窗口	 
	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 Test {

		public static void main(String[] args) {
		Test t=new Test();
		t.set();
		
		}

		private void set() {
			JFrame f=new JFrame();
			f.setTitle("验证码");//窗口标题
			f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//关闭
			f.setExtendedState(JFrame.MAXIMIZED_VERT);//最大化
			f.setSize(300,300);//窗口大小
			Container con=f.getContentPane();
			JPanel pan=new JPanel();
			JLabel yan=new JLabel("验证码：");
			pan.add(yan);
			JTextField yanzhengma=new JTextField(10);
			pan.add(yanzhengma);
			String str = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
			Random random = new Random();
	        StringBuffer yzm = new StringBuffer();
	 
	        for (int i = 0; i < 4; ++i) {
	            int number = random.nextInt(62);// [0,62)
	            yzm.append(str.charAt(number));
	        }
	        String s=yzm.toString();
			JLabel ma=new JLabel(s);
			pan.add(ma);
			 JButton buttenOne=new JButton("确定");
			pan.add(buttenOne);
			
			con.add(pan);
			f.setVisible(true);
			//窗口实现
		}
	}