
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");
}
}