接口(interface)

Final:

　　final的变量的值不能够被改变

　　　　final的成员变量，final的局部变量（形参）

　　final的方法不能被重写

　　final的类不能被继承

接口:

　　1.接口（interface）是抽象方法和常量值的定义的集合

　　2.从本质上讲，接口是一种特殊的抽象类，这种抽象类中只包含常量和方法的定义，

　　   而没有变量和方法的实现

　　3.接口定义举例:

public interface Runner{
          public static final int id = 1;
        
         public  void start();
         public  void run();
         public  void stop();
}

 接口特性:

　　1.多个无关的类可以实现同一个接口

　　2.一个类可以实现多个无关的接口

　　3.与继承关系类似，接口与实现类之间存在多态性。

　　4.接口中声明属性默认为public static final的，也只能是public static final的

　　5.接口可以继承其它的接口，并添加新的属性和抽象方法

　　6.举例

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

interface Painter {
    public void paint();
    public 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;
    
    public String gerString() {
        return name;
    }
    
    Teacher(String name) {
        this.name = name;
    }
    
    public void teach() {
        System.out.println("teaching");
    }
    
    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("steven");
        s2.sing();
        s2.sleep();
        
        Painter p1 = (Painter)s2;
        p1.paint();
        p1.eat();
    }
}


/*
运行结果:
student is singing
student is sleeping
teacher is singing
teacher is sleeping
teacher is painting
teacher is eating
*/