java之接口interface

接口

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、定义java类的语法格式

< modifier> class < name>[extends< superclass>][implements< interface>[, interface]*]{

　　<declarations>*

}

　　

附：

1、接口(interface)是抽象方法和常亮值的定义的结合。

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亮和方法的定义，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 strrt();

    public void run();

    public void stop();

}

 

 

接口特性：

1、接口可以实现多重继承

2、接口声明的属性默认为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、接口可以继承其他接口，并添加新的属性和抽象方法；

 

接口的使用以及接口实现多态：

public class TestInterface{

    public static void main(String args[]){

        Singer student = new Student("studentName");

        student.sing();

        student.sleep();

        

        Teacher teacher = new Teacher("TeacherName");

        teacher.painter();

        teacher.eat();

        

        Painter painter = (Painter)teacher;

        painter.painter();

        painter.eat();

        //下面是实现多态的部分

        TestInterface t1 = new TestInterface();

        t1.f(student);

        t1.f(teacher);

    }

    public void f(Singer s){

        s.sing();

    }

}

interface Singer{

    public void sing();

    public void sleep();

}

interface Painter{

    public void painter();

    public void eat();

}

class Student implements Singer{

    private String name;

    public Student(String name){

        this.name = name;

    }

    public String getName(){

        return name;

    }

    public void Study(){

        System.out.println("studying...");

    }

    public void sing(){

        System.out.println("study is singing");

    }

    public void sleep(){

        System.out.println("study is sleeping");

    }

}

class Teacher implements Singer,Painter{

    private String name;

    public Teacher(String name){

        this.name = name;

    }

    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 painter(){

        System.out.println("teacher is paintering");

    }

    public void eat(){

        System.out.println("teacher is eating");

    }

}

运行结果：

 

内存分析图：

 

 

示例：下面实现了一个三种不同的人给动物喂食和玩的多态，用接口实现。

public class TestDynamic{

    public static void main(String args[]){

        

        HelpAnimal farmer = new Farmer("farmer");

        HelpAnimal worker = new Worker("worker");

        HelpAnimal goverment = new Goverment("goverment");

        

        TestDynamic test = new TestDynamic();

        test.f(farmer);

        test.f(worker);

        test.f(goverment);

        

    }

    public void f(HelpAnimal animal){

            animal.play();

            animal.eat();

    }

}



interface HelpAnimal{

    public void eat();

    public void play();

}



class Farmer implements HelpAnimal{

    private String name;

    public Farmer(String name){

        this.name = name;

    }

    public void eat(){

        System.out.println("Farmer eat");

    }

    public void play(){

        System.out.println("Farmer play");

    }

}



class Worker    implements HelpAnimal{

    private String name;

    public Worker(String name){

        this.name = name;

    }

    public void eat(){

        System.out.println("Worker eat");

    }

    public void play(){

        System.out.println("Worker play");

    }

}



class Goverment    implements HelpAnimal{

    private String name;

    public Goverment(String name){

        this.name = name;

    }

    public void eat(){

        System.out.println("Goverment eat");

    }

    public void play(){

        System.out.println("Goverment play");

    }

}