简易计算器小程序代码：

package jisuanqi;

//声明需要插入的包
import java.awt.*;
import java.lang.Object;
import java.lang.String;
import javax.swing.*;
import java.awt.event.*;
import java.awt.TextComponent;
//声明一个主类jisuanqi，继续窗口类Frame
public class jisuanqi extends Frame{
	
	//声明16个Button
	Button anjian1, anjian2, anjian3, anjian4, anjian5, anjian6, anjian7, anjian8, anjian9, anjian10, anjian11, anjian12, anjian13, anjian14,anjian15,anjian16;
	//声明文本框，用于接收数字和计算
	TextField numText;
	//声明面板容器，用于存放各种按钮
	Panel anjianPanel;
	//构造方法初始化按钮
	jisuanqi(String title){
		
		super(title);
		anjian1=new Button("0");
		anjian2=new Button("1");
		anjian3=new Button("2");
		anjian4=new Button("3");
		anjian5=new Button("4");
		anjian6=new Button("5");
		anjian7=new Button("6");
		anjian8=new Button("7");
		anjian9=new Button("8");
		anjian10=new Button("9");
		anjian11=new Button("+");
		anjian12=new Button("-");
		anjian13=new Button("*");
		anjian14=new Button("/");
		anjian15=new Button("=");
		anjian16=new Button("清空");
		//初始化文本框，将文本的值设置为“0”
		numText=new TextField("0");
		//实例化面板;
		anjianPanel=new Panel();
		//设置按钮
		anjianPanel.setLayout(new FlowLayout());
		//实例化按钮
		anjian1.addActionListener(new anjianAction());
		anjian2.addActionListener(new anjianAction());
		anjian3.addActionListener(new anjianAction());
		anjian4.addActionListener(new anjianAction());
		anjian5.addActionListener(new anjianAction());
		anjian6.addActionListener(new anjianAction());
		anjian7.addActionListener(new anjianAction());
		anjian8.addActionListener(new anjianAction());
		anjian9.addActionListener(new anjianAction());
		anjian10.addActionListener(new anjianAction());
		anjian11.addActionListener(new anjianAction());
		anjian12.addActionListener(new anjianAction());
		anjian13.addActionListener(new anjianAction());
		anjian14.addActionListener(new anjianAction());
		anjian15.addActionListener(new anjianAction());
		anjian16.addActionListener(new anjianAction());
		//将各个按钮添加到面板容器中
		anjianPanel.add(anjian1);
		anjianPanel.add(anjian2);
		anjianPanel.add(anjian3);
		anjianPanel.add(anjian4);
		anjianPanel.add(anjian5);
		anjianPanel.add(anjian6);
		anjianPanel.add(anjian7);
		anjianPanel.add(anjian8);
		anjianPanel.add(anjian9);
		anjianPanel.add(anjian10);
		anjianPanel.add(anjian11);
		anjianPanel.add(anjian12);
		anjianPanel.add(anjian13);
		anjianPanel.add(anjian14);
		anjianPanel.add(anjian15);
		anjianPanel.add(anjian16);
		//为文本框添加事件
		numText.addTextListener(new TextListener() {
			
			public void textValueChanged(TextEvent e) {
				
				if(numText.getText().indexOf("0",0)!=-1){
					
					numText.getText().replace("0","");
				}
			}
		});
		
		addWindowListener(new WindowAdapter() {
			
			public void windowClosing(WindowEvent e) {
				
				System.exit(0);
			}
		});
		//将文本框放置在顶部
		add(numText,BorderLayout.NORTH);
		//添加按钮
		add(anjianPanel,BorderLayout.CENTER);
		//设置文本框属性
		numText.setEditable(false);
	}
	//没有任何操作的值
	int num=0;
	//numStr是文本框的值
	String numStr=null;
	Boolean chinage=false;
	//设置按钮
	public int check(){
	numStr = numText.getText();
	if (numStr.indexOf("+") == 0) {
		
		numStr = numStr.replace(\'+\', \'0\');
		num = num + Integer.parseInt(numStr);
		return num;
	}
	else if (numStr.indexOf("-") != -1) {
		
		numStr = numStr.replace("-", "0");
		num = num - Integer.parseInt(numStr);
		return num;
	}
	else if(numStr.indexOf("*")!=-1){
		
		numStr=numStr.replace(\'*\',\'0\');
		num = num * Integer.parseInt(numStr);
		return num;
	}
	else if(numStr.indexOf("/")!=-1){
		
		numStr=numStr.replace(\'/\',\'0\');
		try{
			
			num = num / Integer.parseInt(numStr);
			return num;
		}
		catch(ArithmeticException e){
			
			JOptionPane.showMessageDialog(null,"除数不能为空!","消息!",1);
			return num;
		}
	}
	else return num=Integer.parseInt(numStr);
	}
	//创建事件
	private class anjianAction implements ActionListener{
		
		public void actionPerformed(ActionEvent event){
		
			if(event.getActionCommand()=="0"){
		
				if(!numText.getText().equals("0"))
					numText.setText(numText.getText()+0);
			}
	
			if(event.getActionCommand()=="1")
				numText.setText(numText.getText()+1);
			if(event.getActionCommand()=="2")
				numText.setText(numText.getText()+2);
			if(event.getActionCommand()=="3")
				numText.setText(numText.getText()+3);
			if(event.getActionCommand()=="4")
				numText.setText(numText.getText()+4);
			if(event.getActionCommand()=="5")
				numText.setText(numText.getText()+5);
			if(event.getActionCommand()=="6")
				numText.setText(numText.getText()+6);
			if(event.getActionCommand()=="7")
				numText.setText(numText.getText()+7);
			if(event.getActionCommand()=="8")
				numText.setText(numText.getText()+8);
			if(event.getActionCommand()=="9")
				numText.setText(numText.getText()+9);
	
			if(event.getActionCommand()=="清空"){
		
				numText.setText("0");
				num=0;
			}
			if(event.getActionCommand()=="+"){
		
				//调用check();方法
				check();
				numText.setText("+");
			}
			if(event.getActionCommand()=="-"){
				
				check();
				numText.setText("-");
			}
			if(event.getActionCommand()=="*"){
		
				check();
				numText.setText("*");
			}
			if(event.getActionCommand()=="/"){
				
				if(numStr=="/0"){
		
					JOptionPane.showMessageDialog(null,"除数不能为空!","消息!",1);
				}
				check();
				numText.setText("/");
			}
			if(event.getActionCommand()=="="){
		
				check();
				numText.setText(""+num);
			}
		}
	}
	public static void main(String[] args){
		
		jisuanqi jisuanqi=new jisuanqi("计算器");
		jisuanqi.setBackground(Color.CYAN);
		jisuanqi.setSize(300,280);
		//设置窗口大小
		jisuanqi.setLocation(550,350);
		//设置界面属性
		jisuanqi.setVisible(true);
	}
}