Java实现计算器的代码

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);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 ArrayList<>();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 = stack.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

/*** 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;}}}