[数据结构与算法]Java计算器2.0

在Java计算器1.0的基础上进行了修改，从原有的变量固定值升级为键盘输入任意double类型的变量值，又新增了calculation方法，减少了main方法中的代码量。

package method;

import java.util.Scanner;

public class Test02 {
    public static void main(String[] args) {
        System.out.println(calculation());
    }
    public static double add(double a, double b){
        return a+b;
    }
    public static double reduce(double a,double b){
        return a-b;
    }
    public static double ride(double a,double b){
        return a*b;
    }
    public static double except(double a,double b){
        if(b==0){
            System.out.println("除数不能为0");
            return 0;
        }else{
            return a/b;
        }
    }
    public static double calculation(){
        double sum=0;
        Scanner sc = new Scanner(System.in);
        Scanner sc2 = new Scanner(System.in);
        Scanner sc1 = new Scanner(System.in);

        System.out.println("请输入数字a");
        double a=sc.nextDouble();
        System.out.println("请输入运算符");
        String f=sc1.next();
        System.out.println("请输入数字b");
        double b=sc2.nextDouble();
        switch (f){//通过对f的判断选择计算方法
            case "+":
                sum=add(a,b);
                break;
            case "-":
                sum=reduce(a,b);
                break;
            case "*":
                sum=ride(a,b);
                break;
            case "/":
                sum=except(a,b);
                break;
            default:
                System.out.println("符号输入错误");
        }
        sc.close();
        sc1.close();
        sc2.close();
        return sum;
    }
}