Java实现计算器（可以计算括号，小数，乘方，以及基本的加减乘除）

package cn.hnh.calculator;

import java.util.Stack;

public class Calculator {
	public static int i = 0;

	public static void main(String[] args) {
		String s = "167.5+3-2+2!-4/2+3^2\0";
		Calculator c = new Calculator();
		StringBuilder RPN = new StringBuilder();
		float temp = c.calculate(s, RPN);
		System.out.println(temp);

	}

	public float calculate(String str, StringBuilder RPN) {
// 新建两个栈，一个存储数据，一个存储操作符
		Stack<Float> numStack = new Stack<>();
		Stack<Character> operStack = new Stack<>();
		char[] oper2 = str.toCharArray();
		operStack.push('\0');
		while (!operStack.isEmpty()) {
			if (isDigit(str)) {
				readNumble(str, numStack);
				RPN.append(numStack.peek());
			} else {
				switch (orderBetween(operStack.peek(), oper2[i])) {
				case '<':
					operStack.push(oper2[i]);
					i++;
					break;
				case '=':
					operStack.pop();
					i++;
					break;
				case '>':
					char temp = operStack.pop();
					RPN.append(temp);
					if (temp == '!') {
						float opNumber = numStack.pop();
						numStack.push(calcu(opNumber, temp));
					} else {
						float opNumber1 = numStack.pop();
						float opNumber2 = numStack.pop();
						numStack.push(calcu(opNumber1, opNumber2, temp));
					}
					
					break;
				default:
					throw new RuntimeException("输入字符有误");

				}
				
			}
		}
		System.out.println(RPN);
		return numStack.pop();
	}

	public boolean isDigit(String str) {
		char[] oper = str.toCharArray();
		if (oper[i] == '0' || oper[i] == '1' || oper[i] == '2' || oper[i] == '3' || oper[i] == '4' || oper[i] == '5'
				|| oper[i] == '6' || oper[i] == '7' || oper[i] == '8' || oper[i] == '9') {
			return true;
		} else {
			return false;
		}
	}

	public void readNumble(String str1, Stack<Float> stack) {
		char[] oper1 = str1.toCharArray();
		stack.push((float) oper1[i] - '0');
		i++;
		while (isDigit(str1)) {
			stack.push((float) stack.pop() * 10 + (float) oper1[i] - '0');
			i++;
		}
		if ('.' != (oper1[i])) {
			return;
		} else {
			i++;
			float flaction = 1;
			while (isDigit(str1)) {
				stack.push(stack.pop() + (float) (oper1[i] - '0') * (flaction /= 10));
				i++;
			}
		}
	}

	public char orderBetween(char c1, char c2) {
		return Operate.pri[transfer(c1)][transfer(c2)];
	}

	public int transfer(char c) {
		switch (c) {
		case '+':
			return 0;
		case '-':
			return 1;
		case '*':
			return 2;
		case '/':
			return 3;
		case '^':
			return 4;
		case '!':
			return 5;
		case '(':
			return 6;
		case ')':
			return 7;
		case '\0':
			return 8;
		default:
			throw new RuntimeException("数字输入错误");
		}
	}

	public float calcu(float f1, char temp) {
		if (f1 == 0) {
			return 1;
		} else {
			float data = 1;
			for (float m = 1; m <= f1; m++) {
				data *= m;

			}
			return data;
		}
	}

	public float calcu(float f1, float f2, char temp) {
		switch(temp) {
		case '+':
			return f1+f2;
		case '-':
			return f2-f1;
		case '*':
			return f2*f1;
		case '/':
			return f2/f1;
		case '^':
			return (float) Math.pow(f2, f1);
		default:
			throw new RuntimeException("输入错误");

	}
}
}

package cn.hnh.calculator;

public enum Operate {
	ADD, SUB, MUL, DIV, POW, FAC, L_P, R_P, EOE;
	static char pri[][] = { { '>', '>', '<', '<', '<', '<', '<', '>', '>' }, { '>', '>', '<', '<', '<', '<', '<', '>', '>' },
			{ '>', '>', '>', '>', '<', '<', '<', '>', '>' }, { '>', '>', '>', '>', '<', '<', '<', '>', '>' },
			{ '>', '>', '>', '>', '>', '<', '<', '>', '>' }, { '>', '>', '>', '>', '>', '>', ' ', '<', '>' },
			{ '<', '<', '<', '<', '<', '<', '<', '=', ' ' }, { ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ' },
			{ '<', '<', '<', '<', '<', '<', '<', ' ', '=' }, };
}