Java之抽象abstract关键字

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1.用abstract关键字修饰一个类时，叫抽象类。用abstract关键字修饰一个方法时，叫抽象方法

2.含有抽象方法的类必须被声明为抽象类，抽象类必须被继承，抽象方法必须被重写

3.抽象类不能被实例化

4.抽象方法只需声明，不需实现

5.继承抽象类的也可以是抽象类，重写的抽象方法还是抽象方法

abstract class Animal {private String name;Animal(String name) {this.name = name;}public abstract void enjoy();//System.out.println("animalshout...");}class Cat extends Animal {private String eyesColor;Cat(String n,String c) {super(n);eyesColor = c;}public void enjoy() {System.out.println("catshoult...");}}class Dog extends Animal {private String furColor;Dog(String n,String c) {super(n);furColor = c;}public void enjoy() {System.out.println("dogshoult...");}}class Lady {private String name;private Animal pet;Lady(String name, Animal pet) {this.name = name;this.pet = pet;}public void myPetEnjoy() {pet.enjoy();}}public class TestTai {public static void main(String[] args) {Cat c = new Cat("catname", "blue");Dog d = new Dog("d ogname", "black");Lady l1 = new Lady("l1", c);Lady l2 = new Lady("l2", d);l1.myPetEnjoy();l2.myPetEnjoy();}}

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