java中的接口interface

interface 是一种特殊的类，接口使得Java拥有了C++中多重继承的机制
1.interface类中的成员变量默认是且只能是public static final类型
2.interface类中的成员函数默认是且只能是public类型，且方法默认是abstract方法
3.类实现接口用implement关键字，接口可以继承接口用extends

4.接口类引用可以指向实现接口的子类对象，但是只能看到自己的抽象方法，不能看到子类自己的方法

测试代码：

interface Singer{
void sing();
void sleep();
}

interface Painter{
void paint();
void eat();
}

class Student implements Singer{
private String name;
Student(String name){this.name = name;}

public void study(){System.out.println("studying");}

public String getName(){return name;}

public void sing() {System.out.println("student is singing");}

public void sleep(){System.out.println("student is sleeping");}
}

class Teacher implements Singer,Painter{
private String name;
Teacher(String name){this.name = name;}

public void teach(){System.out.println("teaching");}

public String getName(){return name;}

public void sing(){System.out.println("teacher is singing");}

public void sleep(){System.out.println("teacher is sleeping");}

public void paint(){System.out.println("teacher is painting");}

public void eat(){System.out.println("teacher is eating");}
}

public class TestInterface{
public static void main(String args[]){
Singer s1 = new Student("le");
s1.sing();s1.sleep();
Singer s2 = new Teacher("kitian");
s2.sing();s2.sleep();
Painter p1 = (Painter)s2;
p1.paint();p1.eat();
}
}