Java编程...

import javaawt;

import javalang;

import javaxswing;

import javaxswingevent;

import javaawtevent;

import javatextDecimalFormat;

public class Caculator implements ActionListener { //导入动作监听接口

//设计面板中的单位

JFrame frame;

JTextField textAnswer;

JPanel panel, panel1, panel2, panel3;

JMenuBar mainMenu;

JTextField textMemory;

JLabel labelMemSpace; //labelMemSpace单纯做摆设，控制面板的形状

JButton buttonBk, buttonCe, buttonC;

JButton button[];

JButton buttonMC, buttonMR, buttonMS, buttonMAdd;

JButton buttonDot, buttonAddAndSub, buttonAdd, buttonSub, buttonMul,

buttonDiv, buttonMod;

JButton buttonSqrt, buttonDao, buttonEqual;

JMenu editMenu, viewMenu, helpMenu;

JMenuItem copyItem, pasteItem, tItem, sItem, numberGroup, topHelp, aboutCal;

DecimalFormat df; //设置数据输出精度

boolean clickable; //控制当前能否按键

double memoryd; //使用内存中存储的数字

int memoryi;

double vard, answerd; //用来保存double型数据的中间值(vard)和最后结果(answerd)

short key = -1, prekey = -1; //key用来保存当前进行何种运算,prekey用来保存前次进行何种运算

String copy; //做复制用

JTextArea help; //帮助

JScrollPane scrollHelp;

//构造函数

public Caculator() {

clickable = true;

answerd = 0;

frame = new JFrame("计算器");

df = new DecimalFormat("0##############"); //设置数据输出精度(对于double型值)

textAnswer = new JTextField(15);

textAnswersetText("");

textAnswersetEditable(false);

textAnswersetBackground(new Color(255, 255, 255));

panel = new JPanel();

framegetContentPane()add(panel);

panel1 = new JPanel();

panel2 = new JPanel();

panelsetLayout(new BorderLayout());

//设计整个面板

mainMenu = new JMenuBar();

editMenu = new JMenu("编辑(E)");

viewMenu = new JMenu("查看(V)");

helpMenu = new JMenu("帮助(H)");

copyItem = new JMenuItem(" 复制(C) Ctrl+C");

copyItemaddActionListener(this);

pasteItem = new JMenuItem(" 粘贴(V) Ctrl+V");

pasteItemaddActionListener(this);

editMenuadd(copyItem);

editMenuadd(pasteItem);

tItem = new JMenuItem("●标准型(T)");

tItemaddActionListener(this);

sItem = new JMenuItem(" 科学型(S)");

sItemaddActionListener(this);

numberGroup = new JMenuItem(" 数字分组(I)");

numberGroupaddActionListener(this);

viewMenuadd(tItem);

viewMenuadd(sItem);

viewMenuadd(numberGroup);

topHelp = new JMenuItem(" 帮助主题(H)");

topHelpaddActionListener(this);

help = new JTextArea(5, 20);

scrollHelp = new JScrollPane(help);

helpsetEditable(false);

helpappend("执行简单计算\n");

helpappend("1 键入计算的第一个数字。\n");

helpappend("2 单击“+”执行加、“-”执行减、“”执行乘或“/”执行除。\n");

helpappend("3 键入计算的下一个数字。\n");

helpappend("4 输入所有剩余的运算符和数字。\n");

helpappend("5 单击“=”。\n");

aboutCal = new JMenuItem(" 关于计算器(A)");

aboutCaladdActionListener(this);

helpMenuadd(topHelp);

helpMenuadd(aboutCal);

mainMenuadd(editMenu);

mainMenuadd(viewMenu);

mainMenuadd(helpMenu);

paneladd(mainMenu, BorderLayoutNORTH);

paneladd(textAnswer, BorderLayoutCENTER);

paneladd(panel1, BorderLayoutSOUTH);

panel1setLayout(new BorderLayout());

textMemory = new JTextField(3);

textMemorysetEditable(false);

textMemorysetBackground(new Color(217, 217, 217));

labelMemSpace = new JLabel(" ");

buttonBk = new JButton("Backspace");

buttonBksetForeground(new Color(255, 0, 0));

buttonCe = new JButton("CE");

buttonCesetForeground(new Color(255, 0, 0));

buttonC = new JButton("C");

buttonCsetForeground(new Color(255, 0, 0));

buttonBkaddActionListener(this);

buttonCeaddActionListener(this);

buttonCaddActionListener(this);

panel1add(panel2, BorderLayoutNORTH);

panel2setLayout(new FlowLayout(FlowLayoutRIGHT));

panel2add(textMemory);

panel2add(labelMemSpace);

panel2add(buttonBk);

panel2add(buttonCe);

panel2add(buttonC);

panel3 = new JPanel();

panel1add(panel3, BorderLayoutCENTER);

button = new JButton[10];

for (int i = 0; i < buttonlength; i++) {

button[i] = new JButton(IntegertoString(i));

button[i]setForeground(new Color(0, 0, 255));

}

buttonMC = new JButton("MC");

buttonMCsetForeground(new Color(255, 0, 0));

buttonMR = new JButton("MR");

buttonMRsetForeground(new Color(255, 0, 0));

buttonMS = new JButton("MS");

buttonMSsetForeground(new Color(255, 0, 0));

buttonMAdd = new JButton("M+");

buttonMAddsetForeground(new Color(255, 0, 0));

buttonDot = new JButton("");

buttonDotsetForeground(new Color(0, 0, 255));

buttonAddAndSub = new JButton("+/-");

buttonAddAndSubsetForeground(new Color(0, 0, 255));

buttonAdd = new JButton("+");

buttonAddsetForeground(new Color(255, 0, 0));

buttonSub = new JButton("-");

buttonSubsetForeground(new Color(255, 0, 0));

buttonMul = new JButton("");

buttonMulsetForeground(new Color(255, 0, 0));

buttonDiv = new JButton("/");

buttonDivsetForeground(new Color(255, 0, 0));

buttonMod = new JButton("%");

buttonModsetForeground(new Color(0, 0, 255));

buttonSqrt = new JButton("sqrt");

buttonSqrtsetForeground(new Color(0, 0, 255));

buttonDao = new JButton("1/x");

buttonDaosetForeground(new Color(0, 0, 255));

buttonEqual = new JButton("=");

buttonEqualsetForeground(new Color(255, 0, 0));

//将所有行为与监听绑定

panel3setLayout(new GridLayout(4, 6));

panel3add(buttonMC);

buttonMCaddActionListener(this);

panel3add(button[7]);

button[7]addActionListener(this);

panel3add(button[8]);

button[8]addActionListener(this);

panel3add(button[9]);

button[9]addActionListener(this);

panel3add(buttonDiv);

buttonDivaddActionListener(this);

panel3add(buttonSqrt);

buttonSqrtaddActionListener(this);

panel3add(buttonMR);

buttonMRaddActionListener(this);

panel3add(button[4]);

button[4]addActionListener(this);

panel3add(button[5]);

button[5]addActionListener(this);

panel3add(button[6]);

button[6]addActionListener(this);

panel3add(buttonMul);

buttonMuladdActionListener(this);

panel3add(buttonMod);

buttonModaddActionListener(this);

panel3add(buttonMS);

buttonMSaddActionListener(this);

panel3add(button[1]);

button[1]addActionListener(this);

panel3add(button[2]);

button[2]addActionListener(this);

panel3add(button[3]);

button[3]addActionListener(this);

panel3add(buttonSub);

buttonSubaddActionListener(this);

panel3add(buttonDao);

buttonDaoaddActionListener(this);

panel3add(buttonMAdd);

buttonMAddaddActionListener(this);

panel3add(button[0]);

button[0]addActionListener(this);

panel3add(buttonAddAndSub);

buttonAddAndSubaddActionListener(this);

panel3add(buttonDot);

buttonDotaddActionListener(this);

panel3add(buttonAdd);

buttonAddaddActionListener(this);

panel3add(buttonEqual);

buttonEqualaddActionListener(this);

framesetDefaultCloseOperation(frameEXIT_ON_CLOSE);

framepack();

frameshow();

}

//设置各个按钮行为

public void actionPerformed(ActionEvent event) {

boolean sign = false; //判断是否是double型数参与运算，是为true，不是为false

Object temp = eventgetSource();

try {

//如果按下数据按钮，将按下的按钮代表的数据插入的当前文本框字符串之后

for (int i = 0; i <= 9; i++)

if (temp == button[i] && clickable == true)

textAnswersetText(textAnswergetText() + IntegertoString(i));

//按下''按钮时，判断当前文本框内字符串中含不含''，如果已含，则不允许再插入''

if (temp == buttonDot && clickable == true) {

boolean isDot = false;

if (textAnswergetText()length() == 0)

isDot = true;

for (int i = 0; i < textAnswergetText()length(); i++)

if ('' == textAnswergetText()charAt(i)) {

isDot = true;

break;

}

if (isDot == false)

textAnswersetText(textAnswergetText() + "");

}

if ( (temp == buttonAdd || temp == buttonSub || temp == buttonMul || temp == buttonDiv) && clickable == true) {

//'+' *** 作

if (temp == buttonAdd) {

switch (prekey) {

case 0:

answerd += DoubleparseDouble(textAnswergetText());

break;

case 1:

answerd -= DoubleparseDouble(textAnswergetText());

break;

case 2:

answerd = DoubleparseDouble(textAnswergetText());

break;

case 3:

if (DoubleparseDouble(textAnswergetText()) == 0) {

textAnswersetText("除数不能为零");

clickable = false;

}

else

answerd /= DoubleparseDouble(textAnswergetText());

break;

default:

answerd = DoubleparseDouble(textAnswergetText());

}

textAnswersetText("");

prekey = key = 0;

}

//'-' *** 作

if (temp == buttonSub) {

switch (prekey) {

case 0:

answerd += DoubleparseDouble(textAnswergetText());

break;

case 1:

answerd -= DoubleparseDouble(textAnswergetText());

break;

case 2:

answerd = DoubleparseDouble(textAnswergetText());

break;

case 3:

if (DoubleparseDouble(textAnswergetText()) == 0) {

textAnswersetText("除数不能为零");

clickable = false;

}

else

answerd /= DoubleparseDouble(textAnswergetText());

break;

default:

answerd = DoubleparseDouble(textAnswergetText());

}

textAnswersetText("");

prekey = key = 1;

}

//'' *** 作

if (temp == buttonMul) {

switch (prekey) {

case 0:

answerd += DoubleparseDouble(textAnswergetText());

break;

case 1:

answerd -= DoubleparseDouble(textAnswergetText());

break;

case 2:

answerd = DoubleparseDouble(textAnswergetText());

break;

case 3:

if (DoubleparseDouble(textAnswergetText()) == 0) {

textAnswersetText("除数不能为零");

clickable = false;

}

else

answerd /= DoubleparseDouble(textAnswergetText());

break;

default:

answerd = DoubleparseDouble(textAnswergetText());

}

textAnswersetText("");

prekey = key = 2;

}

//'/' *** 作

if (temp == buttonDiv) {

switch (prekey) {

case 0:

answerd += DoubleparseDouble(textAnswergetText());

break;

case 1:

answerd -= DoubleparseDouble(textAnswergetText());

break;

case 2:

answerd = DoubleparseDouble(textAnswergetText());

break;

case 3:

if (DoubleparseDouble(textAnswergetText()) == 0) {

textAnswersetText("除数不能为零");

clickable = false;

}

else

answerd /= DoubleparseDouble(textAnswergetText());

break;

default:

answerd = DoubleparseDouble(textAnswergetText());

}

textAnswersetText("");

prekey = key = 3;

}

}

//'=' *** 作

if (temp == buttonEqual && clickable == true) {

//如果连续按'=',则进行连续运算

if (prekey == 5) {

if (key == 0) {

answerd += vard;

textAnswersetText(dfformat(answerd));

}

if (key == 1) {

answerd -= vard;

textAnswersetText(dfformat(answerd));

}

if (key == 2) {

answerd = vard;

textAnswersetText(dfformat(answerd));

}

if (key == 3) {

if (DoubleparseDouble(textAnswergetText()) == 0) {

textAnswersetText("除数不能为零");

clickable = false;

}

else {

answerd /= vard;

textAnswersetText(dfformat(answerd));

}

}

}

else {

vard = DoubleparseDouble(textAnswergetText());

if (key == 0) {

prekey = -1;

answerd += DoubleparseDouble(textAnswergetText());

textAnswersetText(dfformat(answerd));

}

if (key == 1) {

prekey = -1;

answerd -= DoubleparseDouble(textAnswergetText());

textAnswersetText(dfformat(answerd));

}

if (key == 2) {

prekey = -1;

answerd = DoubleparseDouble(textAnswergetText());

textAnswersetText(dfformat(answerd));

}

if (key == 3) {

prekey = -1;

if (DoubleparseDouble(textAnswergetText()) == 0) {

textAnswersetText("除数不能为零");

clickable = false;

}

else {

answerd /= DoubleparseDouble(textAnswergetText());

textAnswersetText(dfformat(answerd));

}

}

}

prekey = 5;

}

//'%' *** 作，对第二个 *** 作数除以100

if (temp == buttonMod && clickable == true) {

if (answerd == 0) {

String s = textAnswergetText();

textAnswersetText(s);

}

else {

boolean isDot = false;

for (int i = 0; i < textAnswergetText()length(); i++)

if ('' == textAnswergetText()charAt(i)) {

isDot = true;

break;

}

//如果是double数，除100

if (isDot == true) {

double dtemp = DoubleparseDouble(textAnswergetText());

dtemp = dtemp / 1000;

textAnswersetText(DoubletoString(dtemp));

}

else {

//如果是int数但能被100整除，则去掉末尾两个零

if (IntegerparseInt(textAnswergetText()) % 100 == 0) {

int itemp = IntegerparseInt(textAnswergetText());

itemp /= 100;

textAnswersetText(IntegertoString(itemp));

}

//如果是int数，但不能被100整除，则按double数处理

else {

double dtemp = DoubleparseDouble(textAnswergetText());

dtemp = dtemp / 1000;

textAnswersetText(DoubletoString(dtemp));

}

}

}

}

//开根号运算

if (temp == buttonSqrt && clickable == true) {

String s = textAnswergetText();

if (scharAt(0) == '-') {

textAnswersetText("负数不能开根号");

clickable = false;

}

else

textAnswersetText(DoubletoString(javalangMathsqrt(DoubleparseDouble(textAnswergetText()))));

}

//倒数运算

if (temp == buttonDao && clickable == true) {

if (textAnswergetText()charAt(0) == '0' && textAnswergetText()length() == 1) {

textAnswersetText("零不能求倒数");

clickable = false;

}

else {

boolean isDec = true;

int i, j, k;

String s = DoubletoString(1 / DoubleparseDouble(textAnswergetText()));

for (i = 0; i < slength(); i++)

if (scharAt(i) == '')

break;

for (j = i + 1; j < slength(); j++)

if (scharAt(j) != '0') {

isDec = false;

break;

}

if (isDec == true) {

String stemp = "";

for (k = 0; k < i; k++)

stemp += scharAt(k);

textAnswersetText(stemp);

}

else

textAnswersetText(s);

}

}

//按下'+/-'按钮时处理

if (temp == buttonAddAndSub && clickable == true) {

boolean isNumber = true;

String s = textAnswergetText();

for (int i = 0; i < slength(); i++)

if (! (scharAt(i) >= '0' && scharAt(i) <= '9' || scharAt(i) == '' || scharAt(i) == '-')) {

isNumber = false;

break;

}

if (isNumber == true) {

//如果当前字符串首字母有'-'号,代表现在是个负数,再按下时,则将首符号去掉

if (scharAt(0) == '-') {

textAnswersetText("");

for (int i = 1; i < slength(); i++) {

char a = scharAt(i);

textAnswersetText(textAnswergetText() + a);

}

}

//如果当前字符串第一个字符不是符号，则添加一个符号在首字母处

else

textAnswersetText('-' + s);

}

}

//计算器有关内存 *** 作

//'MC'的 *** 作，将内存清0

if (temp == buttonMC && clickable == true) {

memoryd = memoryi = 0;

textMemorysetText("");

}

//'MS'的 *** 作，将当前文本框内容保存入内存，显示'M'

if (temp == buttonMS && clickable == true) {

boolean isDot = false;

textMemorysetText(" M");

for (int i = 0; i < textAnswergetText()length(); i++)

if ('' == textAnswergetText()charAt(i)) {

isDot = true;

break;

}

//如果是double,则存入memoryd(double存储器)

if (isDot == true) {

memoryd = DoubleparseDouble(textAnswergetText());

memoryi = 0; //保证存储器中存放最新的值

}

//如果是int,则存入memoryi(int存储器)

else {

memoryi = IntegerparseInt(textAnswergetText());

memoryd = 0; //保证存储器中存放最新的值

}

}

//'MR'的 *** 作，将存储器中的信息输出

if (temp == buttonMR && clickable == true) {

if (memoryd != 0)

textAnswersetText(DoubletoString(memoryd));

if (memoryi != 0)

textAnswersetText(IntegertoString(memoryi));

}

//'M+'的功能，将当前文本框里的数据和存储器中数据相加后，再存入存储器

if (temp == buttonMAdd && clickable == true) {

boolean isDot = false;

for (int i = 0; i < textAnswergetText()length(); i++)

if ('' == textAnswergetText()charAt(i)) {

isDot = true;

break;

}

if (memoryi != 0) { //存储中是一个int型数

if (isDot == false) //被加数是一个int型数

memoryi += IntegerparseInt(textAnswergetText());

else { //被加数是一个double型数，则将int存储器中数传入double存储器与当前数相加，int存储器清零

memoryd = memoryi + DoubleparseDouble(textAnswergetText());

memoryi = 0;

}

}

else

memoryd += DoubleparseDouble(textAnswergetText());

}

//按下'Backspace'键，利用循环将当前字符串中的最后一个字母删除

if (temp == buttonBk && clickable == true) {

String s = textAnswergetText();

textAnswersetText("");

for (int i = 0; i < slength() - 1; i++) {

char a = scharAt(i);

textAnswersetText(textAnswergetText() + a);

}

}

//按下'CE'按钮，将当前文本框内数据清除

if (temp == buttonCe) {

textAnswersetText("");

clickable = true;

}

//按下'C'按钮，文本框内数据清除，同时var,answer清0

if (temp == buttonC) {

vard = answerd = 0;

textAnswersetText("");

clickable = true;

}

//按下'复制'菜单栏

if (temp == copyItem) {

copy = textAnswergetText();

}

//按下'粘贴'菜单栏

if (temp == pasteItem) {

textAnswersetText(copy);

}

if (temp == sItem) {

JOptionPaneshowMessageDialog(panel, "当前是标准型计算器，\n科学型计算器有待更新。");

}

//按下'帮助主题'菜单栏

if (temp == topHelp) {

JOptionPaneshowMessageDialog(panel, scrollHelp);

}

//按下'数字分组'菜单栏

if (temp == numberGroup) {

if (numberGroupgetText()compareTo(" 数字分组(I)") == 0)

numberGroupsetText("√数字分组(I)");

else

numberGroupsetText(" 数字分组(I)");

}

//按下'关于'菜单栏

if (temp == aboutCal) {

JOptionPaneshowMessageDialog(panel, "计算器100版\n开发者：楼竞");

}

} catch (Exception e) { //输入中如果有 *** 作非法，比如按下两次'+'，捕获异常

textAnswersetText(" *** 作非法");

clickable = false;

}

}

//主函数

public static void main(String args[]) {

new Caculator();

}

}

导入javautilregex下所有的包。

java中的包就像C中的头文件

和C语言中的#include 类似的，都是可以引入系统已经写好的包，或者是模块，当然也可以引入自己写的包或者模块。

问题补充

包里面提供了的功能你就可以直接调用，比如 math 包里面的sqrt函数（开根号的）。但是regex中是否有分母计算的功能就需要查看包的文档了。

public static double sqrt (double c) {

if (c < 0) return DoubleNaN;

double err = 1e-15;

double t = c;

while( Mathabs(t - c/t) > err t)

t = (c/t + t) /20;

return t;

}

手工开根号法,只适用于任何一个整数或者有限小数开二次方

因为网上写不出样式复杂的计算式,所以只能尽量书写,然后通过口述来解释:

假设一个整数1456456,开根号首先要从个位开始,每两位数做个标记,这里用'表示,那么标记后变成1'45'64'56然后根据你要开的小数位数在小数点后补0,这里的举例开到整,则补2个0,(原因等明白该做法后自会理解),解法如下:

解法中需要说明的几个问题:

1,算式中的没有意义,是因为网上无法排版,为了能把版式排得整齐点而加上的

2,为了区别小数点，所以小数点用。表示，而所有的都是为了排版需要

3、除了1'45'64'56中的'有特殊意义，在解题中有用处外，其他的'都是为了排版和对起位置，说明数字来源而加的，取消没有任何影响

1206。8

-----------------------

1/1'45'64'5600(1)

1

--------

22|45(2)

44

--------

240|1'64(3)

0

---------

2406|1'64'56(4)

1'44'36

-----------

24128|20'20'00(5)

19'29'74

----------

10'26

其中第(1)步的意思是对左起第一个'号前的数字进行开方,即本题中的1进行开方并将数字写在上面

第(2)步的意思是将第二个'号和第一个'号之间的数字,即45,写下来作为被除数,把上一步已经得到并写在上面的数字1乘以20作为除数的一部分,另一部分就得通过判断,得到一个数字a,使得除数为(120+a),同时商也为a,本步骤中,判断得到a应为2,所以除数是22,而2作为商写到了上面,1的右边

第(3)步,把上一步除法计算的余数1移下来,同时把第三个'号和第二个'号之间的数字64也移下来,组成数字164作为被除数,然后重复上面的方法,把之前写到上面的数字12乘以20再加上一个可以作为本步骤的商的数字,组成除数因为经过判断,本步骤只有0符合条件,所以除数是240,而商是0写到上面,164作为余数向下移

第(4)步,如果前面能看懂的话,这一步其实只是前面的重复,把164和56都移下来组成被除数16456,然后120乘以20再加上6组成除数,同时6本身就是商,得到余数2020

第(5)步依然是重复,需要特殊说明的是,对于小数点后面的数字,用0补位数就可以了,依然是两位加个'号,做法不变

上面就是基本步骤了,总结起来就是先分位数,然后对第一个分位数字进行开方,如果有余数就想下移,和第二个分位组成被除数而除数是之前已经得到的商乘以20加上某数字组成,而这个数字要在这个步骤中作为商出现的,所以这个数字是0-9中的哪个数字,得进行心算或口算来判断,得到余数再下移,一直重复到得到答案

其中还要说明的是每一步得到的余数一定不能比除数大,也不能小于0,不然是无效的,说明选择做商的数字是不对的

因为1/3，分母，分子都是整型，结果就是取整，所以是0，于预期不符；

如果分母或分子为浮点型，则结果就是浮点型，就是033333等，于预期相符

故应该这样，采纳即可

import javautilScanner;

public class Test {

/

@param args

/

public static void main(String[] args) {

String str2="";

do{

Systemoutprint("请输入需求和的数字，以+号相连=号结尾如（1+1=）");

Scanner sc=new Scanner(Systemin);

try{

String str=scnext();

int num=0;

String str1[]=strsplit("\\+");

for(int i=0;i<str1length;i++){

if(i==str1length-1){

str1[i]=str1[i]substring(0,1);

}

num=num+IntegerparseInt(str1[i]);

}

Systemoutprint(str+""+num);

}catch(Exception e){

Systemoutprint("输入不合法！");

}

Systemoutprint("是否继续？（y/n）");

str2=scnext();

}

while("y"equals(str2));

}

}

只是个加，希望可以帮到你。

结果是：

13 17 19 23 29

31 37 41 43 47

53 59 61 67 71

73 79 83 89 97

程序的功能是：

      输出100以内的所有质数

两种方法：

第一种：写计算圆形，长方形，正方形的函数3个

float calculate1（）；

float calculate2（）；

float calculate3（）；

在你的主程序你做一个switch case判断 就行了

第二种是写一个虚基类calculate然后分别写3个继承自这个基类的计算圆形类，计算长方形类，计算正方形类 在主函数中调用就行了

#include<iostream>

#include<cmath> //因为用到了sqrt()函数，sqrt()为开根号

using namespace std;

int main()

{

cout<<"1计算圆面积"<<endl

<<"2计算矩形面积"<<endl

<<"3计算三角形面积"<<endl

<<"4退出"<<endl

<<"请选择相应程序代码:";

int x; //x对应编号

cin>>x;

double area;

while(x!=4) //当x!=4时循环，即当x=4时退出循环

{

if(x==1)

{

double r;

cout<<"半径:";

cin>>r;

area=314rr;

cout<<"面积为 "<<area<<endl;

}

else if(x==2)

{

double a,b;

cout<<"长和宽:";

cin>>a>>b;

area=ab;

cout<<"面积为 "<<area<<endl;

}

else if(x==3)

{

double a,b,c,d;

cout<<"三边长:";

cin>>a>>b>>c;

d=05(a+b+c);

area=sqrt(d(d-a)(d-b)(d-c));

cout<<"面积为 "<<area<<endl;

}

else

cout<<"输入有误，请重新输入!"<<endl;

cout<<"程序代码:";

cin>>x;

}

return 0;

}

可以对选择的图形做判断后计算面积