ch12_4_1.java

java练习程序

import java.applet.*;
import java.awt.*;
import java.awt.event.*;

public class Ch12_4_1 extends Applet implements ActionListener
{
	Label Label_1,Label_2,Label_3,Label_4;
	TextField text1,text2,text3;
	Button Btn;
	GridLayout net;
	public void init()
	{
		net=new GridLayout(3,1);
		setLayout(net);
		
		
		
		
		
		(mypanel2.Btn).addActionListener(this);
	}
	public void actionPerformed(ActionEvent e)
	{
		if(e.getSource()==(mypanel2.Btn))
		{
			long n1,n2,sum=0;
			n1=Long.parseLong(mypanel2.text1.getText());
			n2=Long.parseLong(mypanel2.text2.getText());
			for(long i=n1;i<=n2;i++)
			{
				sum+=i;
			}
			mypanel3.text1.setText(String.valueOf(sum));
		}
	}
}
class Mypanel1 extends Panel
{
	Label Label1;
	Mypanel1()
	{
		setLayout(new GridLayout(1,1));
		Label1=new Label("计算从数a到b的连续和",Label.CENTER);
		add(Label1);
	}
}

class Mypanel2 extends Panel
{
	Label Label1,Label2;
	TextField text1,text2;
	Button Btn;
	Mypanel2()
	{
		Label1=new Label("输入起始数a:");
		Label2=new Label("输入终止数b:");
		text1=new TextField(10);
		text2=new TextField(10);
		Btn=new Button("确定");
		setLayout(new GridLayout(1,5));
		add(Label1);add(text1);add(Label2);add(text2);add(Btn);
	}
}

class Mypanel3 extends Panel
{
	Label Label1;
	TextField text1;
	Mypanel3()
	{
		Label1=new Label("计算结果:");
		text1=new TextField(10);
		setLayout(new GridLayout(1,3));
		add(Label1);add(text1);add(new Label());
	}
}