(学习java)利用顺序栈简易计算器的编写

import java.util.Arrays;import java.util.Scanner;//简易计算器的编写 //中缀表达式转后缀表达式  ,得出结果用于逆波兰数输出//例如 输入:(11+2.2)*3.1+(30*45)-((1.1+23)*3.3)/5.2//转换成后缀表达式: 11 2.2 + 3.1 * 30 45 * + 1.1 23 + 3.3 * 5.2 / - //输出结果:1375.6257692307693public class TurnRPN {public static void main(String[] args) {char[] s = getChar();String expression = getExpression(s);System.out.print("转换成后缀表达式: ");System.out.println(expression);//将字符串转换成字符数组char[] s2 = expression.toCharArray();ArrStack as = rpn(s2);System.out.print("输出结果:");as.listStack();}// 将输入的字符串转换成字符数组public static char[] getChar() {Scanner sc = new Scanner(System.in);// 将输入的字符串转换成一个字符数组System.out.println("请输入中缀表达式(请不要输入空格): ");char[] s = sc.nextLine().toCharArray();return s;}// 中缀表达式转后缀表达式public static String getExpression(char[] s) {ArrStack as = new ArrStack();// 创建字符串存储后缀表达式String arr = "";for (int i = 0; i < s.length; i++) {// 如果是数字或者.直接放入字符串中if (isNumber(s[i]) || s[i] == '.') {arr = arr + s[i];// 判断数字是否完全输入,如果全部输入完毕,则在后面加上空格if (i != s.length - 1) {if (!isNumber(s[i + 1]) && s[i + 1] != '.') {arr = arr + " ";}} else {// 如果字符的最后一位是数字,则直接加空格(与最后出栈的运算符字符区分)arr = arr + " ";}// 如果是运算符字符,则判断后入栈} else if (s[i] == '+' || s[i] == '-' || s[i] == '*' || s[i] == '/') {// 如果是= -则判断栈顶元素是否为 * / 如果是,先将栈顶元素出栈后再入栈 否则,直接入栈if (s[i] == '+' || s[i] == '-') {if (!as.isEmpty()) { // 判断栈是否为空char r = as.getTop();while (r == '+' || r == '-' || r == '*' || r == '/') {r = as.stackPop();arr = arr + r + " ";// 如果栈为空,则直接跳出循环if (!as.isEmpty()) {r = as.getTop();} else {break;}}}as.stackPush(s[i]);} else {as.stackPush(s[i]);}// 如果字符是(直接入栈,如果)则栈顶元素依次出栈,直到出栈元素是(为止} else if (s[i] == '(') {as.stackPush(s[i]);} else if (s[i] == ')') {char r = as.stackPop();while (r != '(') {arr = arr + r + " ";r = as.stackPop();}}}// 将栈中剩余的元素依次存入字符串中while (!as.isEmpty()) {char r = as.stackPop();arr = arr + r + " ";}return arr;}// 逆波兰表达式求值public static ArrStack rpn(char[] s) {ArrStack as = new ArrStack();double num = 0;// 定义空字符串存入字符String arr = "";double a = 0;double b = 0;double result = 0;for (int i = 0; i < s.length; i++) {// 如果是数字或者.则推入栈中if (isNumber(s[i]) || s[i] == '.') {arr = arr + s[i];} else if (s[i] == ' ') {// 遇到空格,将数据取出转成double类型推入栈中if (arr == "") {continue;} else {num = Double.valueOf(arr);as.stackPush(num);// 字符串置空arr = "";}} else {// 遇到运算符字符,弹出栈顶前两个数进行运算后再压入栈中switch (s[i]) {case '+':a = as.stackPop();b = as.stackPop();result = b + a;as.stackPush(result);break;case '-':a = as.stackPop();b = as.stackPop();result = b - a;as.stackPush(result);break;case '*':a = as.stackPop();b = as.stackPop();result = b * a;as.stackPush(result);break;case '/':a = as.stackPop();b = as.stackPop();if (a == 0) {System.out.println("除数不能为0!");break;}result = b / a;as.stackPush(result);break;}}}return as;}// 判断字符是否为数字public static boolean isNumber(char c) {if (c >= 48 && c <= 57) {return true;}return false;}// 创建顺序栈public static class ArrStack {// 定义数组保存元素private Object[] elementData;// 定义栈的当前长度private int size;// 定义栈的当前容量private int capacity;// 定义栈顶public int top;// 初始化,默认建立一个容量为50的数组public ArrStack() {elementData = new Object[50];capacity = 50;}// 初始化,自定义容量数组public ArrStack(int n) {elementData = new Object[n];capacity = n;}// 入栈public <T> void stackPush(T data) {// 如果容量满了,则新建一个数组扩充容量if (size >= capacity) {int newLength = (capacity * 3 / 2) + 1;elementData = Arrays.copyOf(elementData, newLength);capacity = newLength;}elementData[top] = data;top++;size++;}// 出栈public <T> T stackPop() {if (size == 0) {System.out.println("当前为空栈");return null;} else {T data = (T) this.elementData[top - 1];top--;size--;return data;}}// 遍历栈public void listStack() {if (size == 0) {System.out.println("空栈");} else if (size == 1) {System.out.println(elementData[top - 1]);// System.out.println("栈的长度" + size);} else {for (int i = 0; i < size; i++) {System.out.print(elementData[i] + " ");}System.out.println("栈的长度" + size);}}// 返回当前容量public void capacity() {System.out.println("当前最大容量" + capacity);}// 返回当前栈顶的值public <T> T getTop() {T data = (T) elementData[top - 1];return data;}// 判空public boolean isEmpty() {return size == 0;}}}