JAVA基础-抽象类

1. 用abstract关键字来修饰一个类时, 这个类叫做抽象类, 用abstract修饰一个方法时, 该方法叫做抽象方法

2. 含有抽象方法的类必须被声明为抽象类,

3. 抽象类必须被继承, 抽象方法必须被重写

4. 抽象类不能被实例化

5. 抽象方法只需声明, 不需要实现.

如果派生类派生了个抽象子类不想实现抽象方法, 可以将自己设定为abstract,可以不用重写抽象方法, 让继承他的子类再去重写方法.

abstract class Animal {
private String name;
Animal(String name) {this.name = name;}
public abstract void enjoy();
}

class Cat extends Animal {
private String eyesColor;
Cat(String n,String c) {super(n); eyesColor = c;}

public void enjoy() {
System.out.println("猫叫声......");
}
}

class Dog extends Animal {
private String furColor;
Dog(String n,String c) {super(n); furColor = c;}

public void enjoy() {
System.out.println("狗叫声......");
}
}

class Bird extends Animal {
Bird() {
super("bird");
}
public void enjoy() {
System.out.println("鸟叫声......");
}
}

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 Test {
public static void main(String args[]){
Cat c = new Cat("catname","blue");
Dog d = new Dog("dogname","black");
Bird b = new Bird();
Lady l1 = new Lady("l1",c);
Lady l2 = new Lady("l2",d);
Lady l3 = new Lady("l3",b);
l1.myPetEnjoy();
l2.myPetEnjoy();
l3.myPetEnjoy();
}
}