CheckExpression.java

package com.zejian.structures.Stack;

/**
 * Created by zejian on 2016/11/27.
 * Blog : http://blog.csdn.net/javazejian [原文地址,请尊重原创]
 * 表达式检测
 */
public class CheckExpression {

    public static String isValid(String expstr)
    {
        //创建栈
        LinkedStack<String> stack = new LinkedStack<>();

        int i=0;
        while(i<expstr.length())
        {
            char ch=expstr.charAt(i);
            i++;
            switch(ch)
            {
                case '(': stack.push(ch+"");//左括号直接入栈
                    break;
                case ')': if (stack.isEmpty() || !stack.pop().equals("(")) //遇见右括号左括号直接出栈
                    return "(";
            }
        }
        //最后检测是否为空,为空则检测通过
        if(stack.isEmpty())
            return "check pass!";
        else
            return "check exception!";
    }

    public static void main(String args[])
    {
        String expstr="((5-3)*8-2)";
        System.out.println(expstr+"  "+isValid(expstr));
    }
}