【java】接口

public class Test {
    public static void main(String[] args){
        Math shixian = new Shixian();

        System.out.println(shixian.sum(4,3));

        System.out.println(((Ham)shixian).sub(5,4));

        ((Xiaoxue)shixian).xiaoxue();
    }
}

interface Math{
    double PI = 3.14;  //public static final double PI = 3.14;
    int sum(int i, int j);  //public abstract int sum(int i,int j);
}

interface Ham{
    int sub(int i,int j);
}
class Xiaoxue{

    public  void xiaoxue(){
        
    }
}

class Shixian extends Xiaoxue implements Math,Ham{

    public int sum(int i, int j){   //实现接口中的抽象方法时，需要添加public修饰符
        return i+j;
    }
    public int sub(int i,int j){
        return i+j;
    }
    public void xiaoxue(){
        System.out.println("小学生加减法！");
    }
}