Java之interface關鍵字

接口是抽象方法和常量值的定義的集合

從本質上講，接口是一種特殊的抽象類，這種抽象類中只包含常量和方法的定義，而沒有變量和方法的實現

接口中的 方法默認用abstract修飾

接口中的 成員變量默認用public static finalt修飾

接口還可以繼承其他的接口，並添加新的屬性和方法

典型接口：

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

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("singing");
	}
	public void sleep() {
		System.out.println("sleeping");
	}
}
class Teacher implements Singer, Painter {
	private String name;
	Teacher(String name) {
		this.name = name;
	}
	public void study() {
		System.out.println("studying");
		
	}
	public String getName() {
		return name;
	}
	
	public void sing() {
		System.out.println("singing");
	}
	public void sleep() {
		System.out.println("sleeping");
	}
		public void paint() {
		System.out.println("painting");
	}
	public void eat() {
		System.out.println("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();
		
	}
}

一個接口暴露一個對象的一部分方法！！！