Java实现计算器的代码

Java实现计算器的代码

用java 实现的计算器，原理看代码注释，具体内容如下

public class MyCalculator {

public static void main(String[] args) {

String obj = "6+(8/2)+6/3+1*8 + 30";

ArrayList arrayList = strFormat(obj);

System.out.println(obj + "=" + calculator(arrayList));

}

/**

* 采用后续表达式计算结果

* 1、当前字符串为数字时，直接入栈

* 2、当前字符串为计算符时，取出栈中的前两个计算

* 3、将计算结果再放入到栈中，栈中最后剩余的一个元素就是要求的结果

*/

private static int calculator(ArrayList obj) {

ArrayList result = transform(obj);

System.out.println(result);

Stack stack = new Stack<>();

for (int i = 0; i < result.size(); i++) {

String symbol = result.get(i);

if (isDigital(symbol)) { //数字直接入栈

stack.push(Integer.parseInt(symbol));

} else { // 处理操作符

int num1, num2;

num1 = stack.pop(); //取出两个数

num2 = stack.pop();

switch (symbol) {

case "+":

stack.push(num2 + num1);

break;

case "-":

stack.push(num2 - num1);

break;

case "*":

stack.push(num2 * num1);

break;

case "/":

stack.push(num2 / num1);

http:// break;

default:

break;

}

}

}

return stack.pop();

}

/**

* 中序遍历改为后续遍历

*/

private static ArrayList transform(ArrayList arrayList) {

Stack stack = new Stack<>();

ArrayList result = new ArrayLhttp://ist<>();

for (int index = 0; index < arrayList.size(); index++) {

String symbol = arrayList.get(index);

if (isDigital(symbol)) { //如果是数字直接输出

result.add(symbol);

} else if (symbol.equals(")")) {

String tmp;

while (!(tmp = BQKmSoOstack.pop()).equals("(")) { // 匹配成功后停止

result.add(tmp);

}

} else {

if (stack.isEmpty()) {

stack.push(symbol);

continue;

}

String tmp = stack.peek();

while (outPriority(symbol) <= inPriority(tmp)) { //优先级小于栈内优先级，一直出栈

result.add(tmp);

stack.pop();

if (stack.isEmpty()) {

break;

}

tmp = stack.peek();

}

stack.push(symbol);

}

}

//将剩余的出栈

while (!stack.isEmpty()) {

result.add(stack.pop());

}

return result;

}

/**

* 首先对String 进行格式化 转化成ArrayList

* @param src 3*5+8;

* @return ArrayList 3 * 5 + 8

*/

private static ArrayList strFormat(String src) {

if (src == null || src.equals("")) {

return null;

}

ArrayList arrayList = new ArrayList<>();

StringBuilder comChar = new StringBuilder();

for (int i = 0; i

char ch = src.charAt(i);

if (ch == ' ') {

continue; //去除空格

}

if (!Character.isDigit(ch)) {

if (!comChar.toString().trim().equals("")) {

arrayList.add(comChar.toString().trim());

comChar.delete(0, comChar.length());

}

arrayList.add(ch + "");

continue;

}

comChar.append(ch);

}

if (!comChar.toString().trim().equals("")) {

arrayList.add(comChar.toString().trim());

}

return arrayList;

}

/**

* 判断是否为数字

* @param symbol 782 或者 + - * /

* @return true or false

*/

private static boolean isDigital(String symbol) {

return !symbol.equals("+") && !symbol.equals("-")

&& !symbol.equals("*") && !symbol.equals("/")

&& !symbol.equals("(") && !symbol.equals(")");

}

private static int inPriority(String ch) {

switch (ch) {

case "+":

case "-":

return 2;

case "*":

case "/":

return 4;

case ")":

return 7;

case "(":

return 1;

default:

return 0;

}

}

private static int outPriority(String ch) {

switch (ch) {

case "+":

case "-":

return 3;

case "*":

case "/":

return 5;

case ")":

return 1;

case "(":

return 7;

default:

return 0;

}

}

}

char ch = src.charAt(i);

if (ch == ' ') {

continue; //去除空格

}

if (!Character.isDigit(ch)) {

if (!comChar.toString().trim().equals("")) {

arrayList.add(comChar.toString().trim());

comChar.delete(0, comChar.length());

}

arrayList.add(ch + "");

continue;

}

comChar.append(ch);

}

if (!comChar.toString().trim().equals("")) {

arrayList.add(comChar.toString().trim());

}

return arrayList;

}

/**

* 判断是否为数字

* @param symbol 782 或者 + - * /

* @return true or false

*/

private static boolean isDigital(String symbol) {

return !symbol.equals("+") && !symbol.equals("-")

&& !symbol.equals("*") && !symbol.equals("/")

&& !symbol.equals("(") && !symbol.equals(")");

}

private static int inPriority(String ch) {

switch (ch) {

case "+":

case "-":

return 2;

case "*":

case "/":

return 4;

case ")":

return 7;

case "(":

return 1;

default:

return 0;

}

}

private static int outPriority(String ch) {

switch (ch) {

case "+":

case "-":

return 3;

case "*":

case "/":

return 5;

case ")":

return 1;

case "(":

return 7;

default:

return 0;

}

}

}

版权声明：本文内容由网络用户投稿，版权归原作者所有，本站不拥有其著作权，亦不承担相应法律责任。如果您发现本站中有涉嫌抄袭或描述失实的内容，请联系我们jiasou666@gmail.com 处理，核实后本网站将在24小时内删除侵权内容。