java中的接口interface

不念不忘少年蓝@ 2022-04-06 09:12 269阅读 0赞

# java中的接口interface #

接口（interface）是抽象方法和常量值的定义的集合。

从本质上讲，接口是一种特殊的抽象类，这种抽象类值包含方法和常量的定义，没有变量和方法的实现。

TestInterface.java

//唱歌的接口
    interface Singer {
    	//唱歌
    	public void sing();
    	//睡觉
    	public void sleep();
    }
    
    //画画的接口
    interface Painter {
    	//画画
    	public void paint();
    	//吃饭
    	public void eat();
    }
    
    //学生类实现Singer接口
    class Student implements Singer {
    	//成员变量
    	private String name;
    	
    	//构造方法
    	Student(String name) {
    		this.name = name;
    	}
    	
    	//get set方法
    	public String getName() {
    		return name;
    	}
    	
    	public void setName(String name) {
    		this.name = name;
    	}
    	
    	//自定义方法——学
    	public void study() {
    		System.out.println("studying...");
    	}
    	
    	//重写，实现Singer接口里面的方法
    	//唱歌
    	public void sing() {
    		System.out.println("student is singing...");
    	}
    	//睡觉
    	public void sleep() {
    		System.out.println("student is sleeping...");
    	}
    }
    
    //教师类实现Singer，Painter接口
    class Teacher implements Singer, Painter {
    	//成员变量
    	private String name;
    	
    	//构造方法
    	Teacher(String name) {
    		this.name = name;
    	}
    	
    	//get set方法
    	public String getName() {
    		return name;
    	}
    	
    	public void setName(String name) {
    		this.name = name;
    	}
    	
    	//自定义方法——教
    	public void teache() {
    		System.out.println("teaching...");
    	}
    	
    	//重写，实现Singer接口里面的方法
    	//唱歌
    	public void sing() {
    		System.out.println("teacher is singing...");
    	}
    	
    	//睡觉
    	public void sleep() {
    		System.out.println("teacher is sleeping...");
    	}
    	
    	//重写，实现Painter接口里面的方法
    	//画画
    	public void paint() {
    		System.out.println("teacher is painting...");
    	}
    	
    	//吃饭
    	public void eat(){
    		System.out.println("teacher is eating...");
    	}
    	
    }
    
    public class TestInterface {
    	public static void main(String[] args) {
    		//声明Singer接口引用指向Student
    		Singer s1 = new Student("le");
    		s1.sing();
    		s1.sleep();
    		//声明Singer接口引用指向Teacher
    		Singer s2 = new Teacher("steven");
    		s2.sing();
    		s2.sleep();
    		//将Singer转化为Painter
    		Painter p = (Painter)s2;
    		p.paint();
    		p.eat();
    		
    		//测试Student和Teacher的自定义方法
    		Student s = (Student)s1;
    		s.study();
    		Teacher t = (Teacher)s2;
    		t.teache();
    	}
    }

结果：

F:\java>javac TestInterface.java
    
    F:\java>java TestInterface
    student is singing...
    student is sleeping...
    teacher is singing...
    teacher is sleeping...
    teacher is painting...
    teacher is eating...
    studying...
    teaching...
    
    F:\java>

补充：

Valuable.java

//interface接口
    public interface Valuable {
    	public double getMoney();
    }
    
    //interface接口
    interface Protectable {
    	public void beProtected();
    }
    
    //interface接口继承接口
    interface A extends Protectable {
    	void m();
    	void getMoney();
    }
    
    //abstract抽象类
    abstract class Animal {
    	private String name;
    	
    	abstract void enjoy();
    }
    
    //class类继承abstract，实现interface
    class GoldenMonkey extends Animal implements Valuable, Protectable {
    	public double getMoney() {
    		return 10000;
    	}
    	
    	public void beProtected() {
    		System.out.println("live in the room");
    	}
    	
    	public void enjoy() {
    		
    	}
    	
    	public void test() {
    		Valuable v = new GoldenMonkey();
    		v.getMoney();
    		Protectable p = (Protectable)v;
    		p.beProtected();
    	}
    }
    
    //class实现interface
    class Hen implements A {
    	public void m() {}
    	public void beProtected() {}
    	public double getMoney() {
    		return 1.0;
    	}
    	
    	public void getMoney() {}
    
    }