java的抽象类，abstract关键字

怼烎@ 2022-04-06 09:09 214阅读 0赞

# java的抽象类，abstract关键字 #

TestAbstract.java

//抽象类abstract
    //当一个类中含有抽象方法是，类是"残缺的"，用abstract修饰为抽象的类，
    abstract class Animal {
    	private String name;
    
    	Animal(String name) {
    		this.name = name;
    	}
    
    	//抽象方法，只有方法的定义，没有方法的具体实现，抽象方法就是用来重写的
    	public abstract void enjoy();
    
    }
    
    //抽象类不能被实例化
    abstract class Cat extends Animal {
    	private String eyesColor;
    	
    	Cat(String n,String c) {
    		super(n); 
    		eyesColor = c;
    	}
    	
    	//在子类中可以不实现父类的抽象方法，仍为抽象方法，子类也要变为抽象类
    	public abstract void enjoy();
    }
    
    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;//姓名
    	private Animal pet;//宠物Animal类
    	
    	Lady(String name,Animal pet) {
    		this.name = name; 
    		this.pet = pet;
    	}
    	
    	//我的宠物高兴了
    	public void myPetEnjoy(){
    		pet.enjoy();
    	}
    }
    
    public class TestAbstract {
    	public static void main(String args[]){
    		//抽象类Cat不能被实例化
    		//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);
    		
    		//根据实际的对象来确定调用的方法，不是通过引用类型来确定的，不然就就一定调用Animal中的enjoy()方法，
    		//l1.myPetEnjoy();
    		l2.myPetEnjoy();
    		l3.myPetEnjoy();
    	}
    }