e4.java

几个不错的程序 是本人好多天的结果 真的和不错呀 适合java的学习

/**
 * @(#)E4.java
 *
 * Sample Applet application
 *
 * @author 
 * @version 1.00 06/10/04
 */
 
import java.awt.*;
import java.applet.*;
import java.awt.event.*;
public class E4 extends Applet implements ActionListener
{
	TextField text1=null,text2=null;
	public void init() 
	{
		text1=new TextField(18);
		text2=new TextField(18);
		text1.addActionListener(this);
		add(new Label("输入一个数字后，按Enter"));
		add(text1);
		add(text2);
		
	}

	public void actionPerformed(ActionEvent e)
	{
		double a=0.0;
		text2.setText(null);
		try
		{
			a=Double.valueOf(text1.getText()).doubleValue();
			text2.setText(""+Math.sqrt(a));
		}
		catch(NumberFormatException event)
		{
			text2.setText("请输入数字字符");
		}
	}
}