[Java] 接口-01

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;
    int id = 1;
    public void start();
    public void run();
    void stop(); // public void stop();
}

 接口特性
  *1 接口可以多重实现
  *2 接口中声明的属性默认为 public static final 的; 也只能是 public static final的;
  *3 接口中只能定义抽象方法, 而且这些方法默认为public的，也只能是public的。
  *4 接口可以继承其他的接口，并添加新的属性和抽象方法。
  *5 多个无关的类可以实现同一个接口
  *6 一个类可以实现多个无关的接口
  *7 与继承关系类似，接口与实现类之间存在多态性

package com.bjsxt.chap03;

public interface Singer {
    public void sing();
    public void sleep();
}
interface Painter { // 默认 public 不写也是
    public void paint();
    void eat(); // 默认，不写也是 public , 就是 public 
}
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 getName() {
        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");
    }
}

package com.bjsxt.chap03;

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();
    }
}