先入后出的有序列表。可以使用数组模拟，需要数组maxSize，数组，还有表示栈顶的指针。
    应用：计算中缀表达式。需要两个栈。一个数字栈一个符号栈。

    1. package com.linzhongkai.stack;
    3. import java.util.LinkedList;
    5. public class CalcMidExp {
    6.     public static void main(String[] args) {
    7.         String str = "1+2*3+3/5-1";
    8.         System.out.println(calcMidExp(str));
    9.     }
    10.     public static int calcMidExp(String str) {
    11.         int res = 0;
    12.         LinkedList<Integer> stackNum = new LinkedList<>();
    13.         LinkedList<Character> stackChar = new LinkedList<>();
    14.         char[] chars = str.toCharArray();
    15.         for(char ch : chars) {
    16.             //如果是数字
    17.             if (Character.isDigit(ch)) {
    18.                 if (!stackChar.isEmpty()) {
    19.                     if (stackChar.getLast() == '*' ) {
    20.                         int num1 = ch-'0';
    21.                         int num2 = stackNum.removeLast();
    22.                         int chengfa = num1 * num2;
    23.                         stackNum.addLast(chengfa);
    24.                         stackChar.removeLast();
    25.                     } else if (stackChar.getLast() == '/') {
    26.                         int num1 = ch-'0';
    27.                         int num2 = stackNum.removeLast();
    28.                         int chufa = num2 / num1;
    29.                         stackNum.addLast(chufa);
    30.                         stackChar.removeLast();
    31.                     } else {
    32.                         stackNum.addLast(ch-'0'); //转换为数字
    33.                     }
    34.                 } else {
    35.                     stackNum.addLast(ch-'0'); //转换为数字
    36.                 }
    37.             } else {
    38.                 stackChar.addLast(ch);
    39.             }
    40.         }
    41.         while (!stackChar.isEmpty()) {
    42.             char fuhao = stackChar.removeLast();
    43.             if (fuhao == '+') {
    44.                 int num1 = stackNum.removeLast();
    45.                 int num2 = stackNum.removeLast();
    46.                 int jiafa = num1+num2;
    47.                 stackNum.addLast(jiafa);
    48.             }
    49.             if (fuhao == '-') {
    50.                 int num1 = stackNum.removeLast();
    51.                 int num2 = stackNum.removeLast();
    52.                 int jianfa = num2-num1;
    53.                 stackNum.addLast(jianfa);
    54.             }
    55.         }
    56.         res = stackNum.getFirst();
    57.         return res;
    58.     }
    59. }