看看哪里错了 程序说我需要加函数接口

package _12day;

import org.junit.runner.Computer;

public class _Exercise {
    public static void main(String[] args) {
        Computer compute=new Computer() ;


        Computer com = (a , b) -> {
            return b + a;
        };
        com.calc(com,6,9);


        Computer
![img](https://img-mid.csdnimg.cn/release/static/image/mid/ask/436497683436136.png "=600 #left")
 com1 = (a , b) -> {
            return a - b;
        };
        com1.calc(com1,7,2);

        Computer com2= (a , b) -> a * b;
        com2.calc(com2,4,3);

        Computer com3 = (a , b) -> a / b;
        com3.calc(com3,9,3);



    }
}
@FunctionalInterface
interface Compute {
    double compute(double a, double b);

    void calc(Compute com, int i, int i1);
}

@FunctionalInterface 函数式接口里只能有一个方法