输入四则运算的表达式，求解结果算法

题目：输入四则运算的表达式，求解结果算法

思路：用一个栈来存储数字，用另一个栈来存储符号

package test;

import java.util.Scanner;
import java.util.Stack;

public class StrCount {
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		String str = scanner.nextLine();
		int result = strcount(str);
		System.out.println(str + "=" + result);
	}

	private static int strcount(String str) {
		// TODO Auto-generated method stub
		Stack<Integer> numStack = new Stack<Integer>();
		Stack<Character> sybStack = new Stack<Character>();
		// numStack.push(Integer.parseInt(String.valueOf(str.charAt(0))));
		// sybStack.push(str.charAt(1));
		int firstNum = 0;
		int secondNum = 0;
		int result = 0;
		int i = 0;
		String number = "";
		for (i = 0; i < str.length(); i++) {
			if (!String.valueOf(str.charAt(i)).equals("+")
					&& !String.valueOf(str.charAt(i)).equals("-")
					&& !String.valueOf(str.charAt(i)).equals("*")
					&& !String.valueOf(str.charAt(i)).equals("/")) {
				int j = i + 1;
				number = String.valueOf(str.charAt(i));
				while (j < str.length()
						&& !String.valueOf(str.charAt(j)).equals("+")
						&& !String.valueOf(str.charAt(j)).equals("-")
						&& !String.valueOf(str.charAt(j)).equals("*")
						&& !String.valueOf(str.charAt(j)).equals("/")) {
					String iNum = String.valueOf(str.charAt(j));
					number += iNum;
					++j;
				}
				// number +=String.valueOf(str.charAt(i++));
				numStack.push(Integer.parseInt(number));
				i = j - 1;
			} else if (String.valueOf(str.charAt(i)).equals("+")
					|| String.valueOf(str.charAt(i)).equals("-")
					|| String.valueOf(str.charAt(i)).equals("*")
					|| String.valueOf(str.charAt(i)).equals("/")) {
				if (sybStack.isEmpty()) {
					sybStack.push(str.charAt(i));
				} else {
					if ((sybStack.peek().equals('+') || sybStack.peek().equals(
							'-'))
							&& (String.valueOf(str.charAt(i)).equals("*") || String
									.valueOf(str.charAt(i)).equals("/"))) {
						firstNum = Integer.parseInt(String.valueOf(numStack
								.pop()));
						if (String.valueOf(str.charAt(i)).equals("*")) {
							secondNum = Integer.parseInt(String.valueOf(str
									.charAt(++i)));
							result = firstNum * secondNum;
						} else if (String.valueOf(str.charAt(i)).equals("/")) {
							secondNum = Integer.parseInt(String.valueOf(str
									.charAt(++i)));
							result = firstNum / secondNum;
						}
						numStack.push(result);
					} else if ((sybStack.peek().equals('+') || sybStack.peek()
							.equals('-'))
							&& (String.valueOf(str.charAt(i)).equals("+") || String
									.valueOf(str.charAt(i)).equals("-"))) {
						firstNum = Integer.parseInt(String.valueOf(numStack
								.pop()));
						if (String.valueOf(str.charAt(i)).equals("+")) {
							secondNum = Integer.parseInt(String.valueOf(str
									.charAt(++i)));
							result = firstNum + secondNum;
						} else if (String.valueOf(str.charAt(i)).equals("-")) {
							secondNum = Integer.parseInt(String.valueOf(str
									.charAt(++i)));
							result = firstNum - secondNum;
						}
						numStack.push(result);
					} else if ((sybStack.peek().equals('*') || sybStack.peek()
							.equals('/'))
							&& (String.valueOf(str.charAt(i)).equals("*") || String
									.valueOf(str.charAt(i)).equals("/"))) {
						firstNum = Integer.parseInt(String.valueOf(numStack
								.pop()));
						if (String.valueOf(str.charAt(i)).equals("*")) {
							secondNum = Integer.parseInt(String.valueOf(str
									.charAt(++i)));
							result = firstNum * secondNum;
						} else if (String.valueOf(str.charAt(i)).equals("/")) {
							secondNum = Integer.parseInt(String.valueOf(str
									.charAt(++i)));
							result = firstNum / secondNum;
						}
						numStack.push(result);
					} else if ((sybStack.peek().equals('*') || sybStack.peek()
							.equals('/'))
							&& (String.valueOf(str.charAt(i)).equals("+") || String
									.valueOf(str.charAt(i)).equals("-"))) {
						firstNum = Integer.parseInt(String.valueOf(numStack
								.pop()));
						secondNum = Integer.parseInt(String.valueOf(numStack
								.pop()));
						String syb = String.valueOf(sybStack.pop());
						if (syb.equals("*")) {
							result = firstNum * secondNum;
						} else if (syb.equals("/")) {
							result = firstNum / secondNum;
						}
						numStack.push(result);
					}
				}

				// sybStack.push(str.charAt(i));
			}
		}
		if (i == str.length()) {
			firstNum = Integer.parseInt(String.valueOf(numStack.pop()));
			secondNum = Integer.parseInt(String.valueOf(numStack.pop()));
			String syb = String.valueOf(sybStack.pop());
			if (syb.equals("+")) {
				result = firstNum + secondNum;
			} else if (syb.equals("-")) {
				result = firstNum - secondNum;
			} else if (syb.equals("*")) {
				result = firstNum * secondNum;
			} else if (syb.equals("/")) {
				result = firstNum / secondNum;
			}
		}
		return result;
	}
}