package com.homework2;

public class ClassA implements InterfaceA {

    @Override

    public int method(int n) {

        int sum = 0;

        for(int i = 0; i<=n;i++)

        {

            sum+=i;

        }

        return sum;

    }

}

package com.homework2;

public class ClassB implements InterfaceA {

    @Override

    public int method(int n) {

        int sum = 1;

        for(int i = 1; i<=n;i++)

        {

            sum*=i;

        }

        return sum;

    }

}

package com.homework2;

public interface InterfaceA {

    //定义抽象方法

    int method(int n);

}

package com.homework2;

public class E {

    public static void main(String[] args) {

        ClassA a= new ClassA();

        InterfaceA ia= a;

        System.out.println(a.method(10));

        ClassB b= new ClassB();

        InterfaceA ib= b;

        System.out.println(b.method(5));

    }

}