我的第四个程序 java实现加减乘除

import java.util.Scanner;

public class Test {

    public static void main(String [] args) { 

         Scanner sc = new Scanner(System.in); 

System.out.println("请输入算法：");
         String go = sc.next();

System.out.println("请输入第一个数：");
         Double a = sc.nextDouble(); 

System.out.println("请输入第二个数：");
         Double b =  sc.nextDouble();

if(go.equals("+")){
    Double sum = a+b;
    System.out.println("他们的和为"+sum);
}

if(go.equals("-")){
     Double sum = a-b;
    System.out.println("他们的差为"+sum);
}

if(go.equals("*")){
     Double sum = a*b;
    System.out.println("他们的积为"+sum);
}

if(go.equals("/")){
    Double sum = a/b;
    System.out.println("他们的商为"+sum);
}

}
}