java教程 abstract

 java抽象类

java abstract class

有时候，我们需要用到抽象类。比如我们想买水果，但是不确定买的是苹果还是香蕉
Sometimes, we want to abstract a class.For example, We want buy some fruits,but we are not sure we buy apple or pear.

我们抽象出一个类叫水果
Now we can abstract a class named Fruit

水果就作为了一个抽象类和一个父亲类
Fruit is a abstract class and it is a father class.

苹果和梨就作为子类
Apples and pears fruit is child class

注意：我们不能获得一个抽象类的对象 new Fruit() 会发生错误。
note: can not get a new abstract class new Fruit() is wrong

abstract father class
 
public abstract class Fruit {
	public String getColor(String color){
		return color;
	}
 
	public String getWeight(String weight){
		return weight;
	}
}

child class

public class Apple extends Fruit {
	public String getColor(String color){
		System.out.println("color is " + color);
		return color;
	}
 
	public String getWeight(String weight){
		System.out.println("weight is " + weight);
		return weight;
	}
 
	public static void main(String[] args){
		Fruit f = new Apple();
		//Fruit f = new Fruit();   can not get a new abstract class  new Fruit() is wrong
		f.getColor("red");
	}
}

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