四则整数运算(逆波兰java实现)

文章目录

提示：以下是本篇文章正文内容，下面案例可供参考

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主程序模块

package operation;

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

/**
 * @author WangJiaHui
 * @description: about operation
 * @ClassName Test
 * @date 2022/1/19 18:39
 */
public class Test {
    public static void main(String[] args) {
        //用户输入
        Scanner sc = new Scanner(System.in);
        //初步处理剔除用户意外输入的空格,方便逆波兰.
        String str = sc.nextLine().replace(" ","");
        //调用函数
        int i = Dispose.DisposeString(str);
        System.out.println(i);
    }
}

调用Dispose类,用来进行字符串分割

package operation;

import java.util.ArrayList;

/**
 * @author WangJiaHui
 * @description: a RPN expression
 * @ClassName RPN
 * @date 2022/1/19 18:47
 */
public class Dispose {
    //9+(3-1)*3+10/2
    public static int DisposeString(String str) {
        //进一步处理方便后续操作
        char newC;
        //申明字符数组
        ArrayList<String> list = new ArrayList<>();
        int i=0;
        do{
            //9+(3-1)*3+10/2
            newC = str.charAt(i);
            //如果当前字符是符号
            if (newC <= '0' || newC >= '9' ) {
                //将当前符号加入集合
                list.add("" + newC);
                i++;

            } else {
                //开始拼串
                //用来拼串接收多位数字
                String s = "";
                while (i < str.length() && str.charAt(i) >= '0' && str.charAt(i) <= '9') {
                    s += str.charAt(i++);
                }
                list.add(s);
            }
        }while (i < str.length());
        System.out.println(list);
        return RPN.afterPression(list);
    }
}

调用RPN,进行逆波兰处理

package operation;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.Stack;

/**
 * @author WangJiaHui
 * @description: a RPN
 * @ClassName RPN
 * @date 2022/1/20 17:14
 */
public class RPN {
    //[9, +, (, 3, -, 1, ), *, 3, +, 10, /, 2]
    public static int afterPression(ArrayList list) {

        //创建栈,用来逆波兰
        Stack<String> stack = new Stack<>();
        //用来获得逆波兰表达式后的字符串
        ArrayList list1 = new ArrayList();
        //创建迭代器 逆波兰处理
        Iterator<String> itr = list.iterator();
        //逆波兰处理
        while (itr.hasNext()) {
            String ls = itr.next();
            // + ( -
            if (!stack.isEmpty()) {
                switch (ls) {
                    case "+":
                    case "-":
                        if(stack.peek().equals("*") || stack.peek().equals("/")){
                            while (!stack.isEmpty()) {
                                list1.add(stack.pop());
                            }
                        }
                        stack.push(ls);
                        break;
                    case "*":
                    case "/":stack.push(ls);
                        break;
                    case "(":
                        stack.push(ls);
                        break;
                    case ")":
                        String c1 = ls;
                        // + ( -
                        while (!c1.equals("(")) {
                            c1 = stack.pop();
                            list1.add(c1);
                        }
                        break;
                    default:
                        list1.add(ls);
                }
            } else if (ls.equals("+") || ls.equals("-") || ls.equals("*") || ls.equals("(")) {
                stack.push(ls);
            } else list1.add(ls);
        }
        while (!stack.isEmpty()) {
            list1.add(stack.pop());
        }
        list1.remove("(");
        System.out.println(list1);
        return Compute.MathCompute(list1);
    }
}

调用Compute,进行逆波兰计算

package operation;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.Stack;

/**
 * @author WangJiaHui
 * @description: Compute
 * @ClassName Compute
 * @date 2022/1/20 18:57
 */
public class Compute {
    //[9, 3, 1, -, 3, *, +, 10, 2, /, +]
    public static int MathCompute(ArrayList list){

        Iterator<String> itr = list.iterator();

        //保留符号之前的数字
        Stack<Integer> stack = new Stack<>();
        //获取计算结果
        int res;
        int num1,num2;
        while (itr.hasNext()){
            String s = itr.next();
            switch (s){

                //20
                case "+": res = stack.pop()+stack.pop();stack.push(res);break;
                case "-":
                    num1=stack.pop();num2=stack.pop();
                    //9 2 3
                    res = num2-num1;stack.push(res);break;
                case "*":
                    //9 6
                    res = stack.pop()*stack.pop();stack.push(res);break;
                case "/":
                    //15 5
                     num1=stack.pop();num2=stack.pop();
                  try {
                      res = num2/num1;
                      stack.push(res);
                  }catch (Exception e){
                      System.out.println("除数不能为零!");
                      System.exit(-1);
                  }
                break;
                default:stack.push(Integer.parseInt(s));
            }
        }
        return stack.pop();
    }
}

程序运行结果
1.正常处理

2.异常处理