JAVA编写的计算器源代码

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

public class Calculator extends Applet{
TextField tfAnswer; //显示输入和结果的文本域
Button bPoint,bEqual,bPlus,bMinus,bClear,bMulti,bDivision; //运算符按钮
Button[] b=new Button[10]; //数字按钮

String currentOp,preOp; //当前操作和上一步操作
String foreText,backText; //当前输入和上一次输入
boolean isFloat = false; //运算类型标志

public void init() {
Panel panel1=new Panel(); //实例化面板
Panel panel2=new Panel();
Panel panel3=new Panel();

currentOp = new String(""); //实例化各组件
preOp = new String("");
foreText = new String("");
backText = new String("");
tfAnswer = new TextField(8);
setBackground(Color.lightGray); //设置Applet背景色
setForeground(Color.blue); //设置Applet前景色

for(int i=9;i>=0;i--){
b[i]=new Button(Integer.toString(i)); //实例化数字按钮
panel2.add(b[i]); //增加按钮到面板
}

bPoint = new Button("."); //实例化按钮
bEqual = new Button("=");
bEqual.setForeground(Color.red); //设置按钮前景色
bClear = new Button("清除");
bClear.setForeground(Color.red);
bDivision = new Button("/");
bDivision.setForeground(Color.red);
bMulti = new Button("*");
bMulti.setForeground(Color.red);
bMinus = new Button("-");
bMinus.setForeground(Color.red);
bPlus = new Button("+");
bPlus.setForeground(Color.red);

setLayout(new FlowLayout()); //设置布局管理器
panel1.setLayout(new FlowLayout());
panel2.setLayout(new GridLayout(4,3));
panel3.setLayout(new GridLayout(4,1));
panel1.add(tfAnswer); //增加组件到面板
panel1.add(bClear);
panel2.add(bPoint);
panel2.add(bEqual);
panel3.add(bPlus);
panel3.add(bMinus);
panel3.add(bMulti);
panel3.add(bDivision);
add(panel1); //增加组件到Applet
add(panel2);
add(panel3);
}

public boolean action(Event e, Object o) { //事件处理
String s = new String("");
for(int i=0;i<10;i++){
if(e.target==b[i]||e.target==bPoint){ //按钮事件来自于数字按钮和点按钮
if(e.target != bPoint) {
s = (String)o;
doForeText(s); //处理输入
}
if((e.target == bPoint)&&(!isFloat)){ //浮点数输入
isFloat = true; //设置运算标志
s = (String)o;
if(foreText.equals("")){
foreText += "0."; //增加小数点前面0
}
else{
doForeText(s);
}
}
}
}
if(e.target == bClear) {
doClear(); //清除输入
}
if((e.target == bMulti)||(e.target == bDivision)|| (e.target == bPlus)||(e.target == bMinus)) { //处理运算
if(foreText != ""){
currentOp = ((String)o);
doOperator(); //处理运算
}
else {
preOp = ((String)o);
}
}
if(e.target == bEqual) { //等于按钮事件处理
doOperator(); //处理运算
}
return true;
}

public void doOperator(){
double dFore,dBack;
Double d;

if(preOp.equals("")) {
backText = foreText;
foreText = "";
tfAnswer.setText(backText); //显示文本
}
else {
dFore = (new Double(foreText)).doubleValue(); //得到第一输入
dBack = (new Double(backText)).doubleValue(); //得到第二输入
foreText = "";
backText = tfAnswer.getText();

if(preOp.equals("+")) { //加运算处理
d = new Double((dBack + dFore)); //得到运算结果
tfAnswer.setText(d.toString()); //显示运算结果
backText = d.toString();Double.parseDouble(
}
if(preOp.equals("-")) {
d = new Double((dBack - dFore));//得到运算结果
tfAnswer.setText(d.toString()); //显示运算结果
backText = d.toString();
}
if(preOp.equals("*")) {
d = new Double((dBack * dFore));//得到运算结果
tfAnswer.setText(d.toString());//显示运算结果
backText = d.toString();
}
if(preOp.equals("/")) {
if (dFore==0){
tfAnswer.setText("除数不能为0"); //显示出错信息
return;
}
d = new Double((dBack / dFore));//得到运算结果
tfAnswer.setText(d.toString());//显示运算结果
backText = d.toString();
}
}Math.sin();
preOp = currentOp;
}

public void doForeText(String s) {
foreText += s;
tfAnswer.setText(foreText); //显示输入
}

public void doBackText(String s){
backText = foreText;
foreText = "";
tfAnswer.setText(foreText); //显示输入
}

public void doClear() { //清除输入
currentOp = "";
preOp = "";
foreText = "";
backText = "";
isFloat = false;
tfAnswer.setText("");
}
}