练习题：第一行为数值i，接着的i的行为需要输入的算式，每行可能有三个数据或两个数据

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思路：

1. 获取数据，split分割形成数组
2. 将数组传递给一个指定的解析类
   解析类需要根据符号来判断运算类型，进行运算，并且返回结果
3. 输出计算式子以及式子长度

解析类

package calculator;

import java.util.Arrays;

/**
 * @author 青韵
 * @date 2020/3/8 - 18:45
 */
public class Calculator {
    private static char sign;

    public static String calculate(String[] arr) {
        char tempSign;
        int arrStart;

        if (haveSign(arr.length)) {
            sign = arr[0].charAt(0);
            arrStart = 1;
        } else {
            arrStart = 0;
        }
        tempSign = sign;

        int[] ints = Arrays.stream(arr, arrStart, arr.length)
                .mapToInt(Integer::parseInt).toArray();

        return Equation.create(ints[0], ints[1], tempSign).formatEquation();
    }

    private static boolean haveSign(int len) {
        return len == 3;
    }

    private static class Equation {
        private int num1;
        private int num2;
        private char sign;
        private int result;

        public Equation(int num1, int num2, char sign) {
            this.num1 = num1;
            this.num2 = num2;
            this.sign = sign;
        }

        public static Equation create(int num1, int num2, char sign) {
            return new Equation(num1, num2, sign);
        }

        private void calculate() {
            switch (sign) {
                case 'a': {
                    sign = '+';
                    result = num1 + num2;
                } break;
                case 'b': {
                    sign = '-';
                    result = num1 - num2;
                } break;
                case 'c': {
                    sign = '*';
                    result = num1 * num2;
                } break;
                default: result = 0;
            }
        }

        public String formatEquation() {
            calculate();
            return stringFormat();
        }

        private String stringFormat() {
            return "" + num1 + sign + num2 + "=" + result;
        }
    }
}

主方法测试类

package calculator;

import java.util.Scanner;

/**
 * @author 青韵
 * @date 2020/3/8 - 19:23
 */
public class Main {
    public static void main(String[] args){
        String[] arr;

        Scanner input = new Scanner(System.in);
        int totalRow = input.nextInt();
        input.nextLine();
//        System.out.println("total = " + totalRow);

        for (int i = 0; i <= totalRow; i++) {
            System.out.println();

            arr = input.nextLine().split(" ");
//            System.out.println(Arrays.toString(arr));
            String result = Calculator.calculate(arr);

            System.out.println(result);
            System.out.print(result.length());
        }
    }
}