java - java中的构造函数和抽象类

Question

我有一个抽象类 Entity.java 和一个扩展它的类 Magician.java。每当我创建一个 new Magician("Ged", 300);然后调用 System.out.println() 它总是打印 null(0)，我不确定为什么它应该打印 Ged(300)。相关代码如下:

实体字段/构造函数:

public abstract class Entity {

    protected String name;
    protected int lifePoints = 0;

    public Entity(String name, int lifePoints) {
        assert (lifePoints >= 0);
        this.name = name;
        this.lifePoints = lifePoints;
    }

    ...

}

魔术师 字段/构造函数/toString:

public class Magician extends Entity implements SpellCaster {

    public Magician(String name, int lifePoints) {
        super(name, lifePoints);
        // TODO Auto-generated constructor stub
    }

    protected String name;
    protected int lifePoints;

    ...

    public String toString() {
        return name + "(" + lifePoints + ")";
    }

}

主要类:

public static void main(String[]args) {

    Magician m1=new Magician("Ged",300);
    System.out.println(m1.toString());
}

提前致谢。

Answer 1

您正在隐藏子类 Magician 中父类(super class) Entity 的实例字段 name 和 lifePoints .

默认情况下分别设置为 null 和 0。从子类 Magician 中删除那些实例字段声明。

public class Magician extends Entity implements SpellCaster {

   public Magician(String name, int lifePoints) {
    super(name, lifePoints);
    // TODO Auto-generated constructor stub
   }


    ...

    public String toString(){
       return name + "(" + lifePoints + ")";
    }

}