Java---interface（接口）

1.接口是常量值和抽象方法定义的集合

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，没有变量和方法的实现

3.多个无关的类可以实现同一接口

4.一个类可以实现多个无关的接口

5.与继承类似，接口与实现类之间存在着多态性

接口的特性：

接口可以多重实现。

接口中声明的属性默认为public final staic ，也只能是public final static

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

接口也可能继承其它的接口，并且可能添加新的属性和抽象方法

public class TestInterface {

public static void main(String[] args) {
// 多个无关的类实现同一接口
System.out.println("---多个无关的类实现同一接口----");
Singer s1 = new Student("张同学");
s1.sing();
s1.sleep();
Singer s2 = new Teacher("朱老师");
s2.sing();
s2.sleep();

// 一个类实现不同的接口
System.out.println("---一个类实现不同的接口----");
Teacher t1 = new Teacher("张老师");
t1.sing();
t1.sleep();
t1.paint();
t1.eat();
t1.teach();

//多态的实现
System.out.println("---多态的实现----");
Student student=new Student("李同学");
Teacher teacher=new Teacher("吴老师");
f(student);
f(teacher);
}
static void f(Singer s){
s.sing();
s.sleep();
}

}

// 接口
interface Singer {
void sing();

void sleep();
}

interface Painter {
void paint();

void eat();
}

// 实现Singer接口的Student类
class Student implements Singer {
String name;

public Student(String name) {
this.name = name;
}

public void sing() {
System.out.println(name + " is singing...");
}

public void sleep() {
System.out.println(name + " is sleeping...");
}

void study() {
System.out.println(name + " is studying...");
}
}

//实现Singer、Painter接口的Teacher类
class Teacher implements Singer, Painter {
String name;

Teacher(String name) {
this.name = name;
}

public void sing() {
System.out.println(name + " is singing...");
}

public void sleep() {
System.out.println(name + " is sleeping...");
}

public void paint() {
System.out.println(name + " is painting...");
}

public void eat() {
System.out.println(name + " is eating...");
}

public void teach() {
System.out.println(name + " is teaching...");
}

}