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);
}

}
}