Arraylist.get返回哈希代码，而不是班级的字段

Question

我使用Arraylist作为'英雄' - 基类，而战士，法师是派生类。我想通过使用'get'方法返回每个派生类的lifePoints和attackPoints，而我得到这样的东西（我相信它是类的hashCode）。 （i）通过调试，它显示正确的值，但我不知道如何返回它们，所以我想到了没有参数的构造函数 - 失败了。

输出：

Hero 0 is a Warrior@7852e922 
Hero 1 is a Warrior@4e25154f 
Hero 2 is a Magician@70dea4e 
Hero 3 is a Magician@5c647e05 

预期输出：

Hero 0 is a Warrier with -1 lifePoints and 5 attackPoints 
Hero 1 is a Warrier with 5 lifePoints and 2 attackPoints 
Hero 2 is a Magician with 12 lifePoints and 2 spellPoints 
Hero 3 is a Magician with 13 lifePoints and 2 spellPoints 

我的主类的半码

for (int i=0; i<heroes.size(); ++i) { 
System.out.println("Hero "+i+ " is a "+heroes.get(i)); 
} 

我的解决思路：使用构造函数 - 失败。

public Magician() 
    { 
     System.out.println("Magician with " + this.lifePoints +"life points and " +this.attackPoints +" spell points."); 
    } 

这里是所有代码：

Hero-

abstract class Hero { 

    protected int lifePoints; 
    protected int attackPoints; 

    public abstract Hero attack(Hero other); 
    public abstract int lifePoints(); 

} 

法师：

public class Magician extends Hero{ 

    static int count; 

    Magician(int lifePoints, int attackPoints) 
    { 
     this.lifePoints = lifePoints; 
     this.attackPoints = attackPoints; 
     count++; 
    } 

    public Magician() 
    { 
     System.out.println("Magician with " + this.lifePoints +"life points and " +this.attackPoints +" spell points."); 
    } 
    @Override 
    public Hero attack(Hero other) { 
     if(other != null) 
     { 
      if(other instanceof Hero) 
      { 
       other.lifePoints /= this.attackPoints; 
       if(other.lifePoints <= 0) 
       { 
        return new Magician(this.lifePoints,this.attackPoints); 
       } 
      } 
      //Attacking ourselves - Error 
      if(this.equals(other)) 
      { 
       System.out.println("Hero can't attack itself"); 
      } 
     } 
     return null; 
    } 

    @Override 
    public int lifePoints() { 
     return this.lifePoints; 
    } 

    public static int getNoMagician() 
    { 
     return count; 
    } 

} 

战士：

public class Warrior extends Hero 
{ 
    static int count; 

    Warrior(int lifePoints, int attackPoints) 
    { 
     this.lifePoints = lifePoints; 
     this.attackPoints = attackPoints; 
     count++; 
    } 
    public Warrior() 
    { 
     System.out.println("Warrior with " + this.lifePoints +"life points and " +this.attackPoints +" spell points."); 
    } 

    @Override 
    public Hero attack(Hero other) { 
     if(other != null) 
     { 
      //We're attacking a warrior 
      if(other instanceof Warrior){ 
       ((Warrior)other).lifePoints -= this.attackPoints; 

      } 
      //We're attacking a magician 
      if(other instanceof Magician){ 
       ((Magician)other).lifePoints -= (this.attackPoints/2); 
       if(((Magician)other).lifePoints <= (this.lifePoints/2)) 
       { 
        return new Warrior(this.lifePoints,this.attackPoints); 
       } 

      } 
      //Attacking ourselves - Error 
      if(this.equals(other)) 
      { 
       System.out.println("Hero can't attack itself"); 
      } 
     } 
     //False 
     return null; 
    } 

    @Override 
    public int lifePoints() { 
     return this.lifePoints; 
    } 

    public static int getNoWarrior() 
    { 
     return count; 
    } 

} 

Answer 1

对象的默认toString()就是您要调用其哈希码的内容。为了获得您想要的输出，您需要在Hero的每个子类中创建您自己的方法，例如，类魔术师： - 如下

public String getDescription() { 
    return "Magician with " + this.lifePoints +" life points and " +this.attackPoints +" spell points."); 
} 

然后调用这个方法： -

for (int i=0; i<heroes.size(); ++i) { 
    System.out.println("Hero " + i + " is a "+heroes.get(i).getDescription()); 
} 

注意，我不会为了这个目的覆盖toString()，因为这种方法通常用于调试。如果其他人编辑你的代码，他们可能会改变toString（）输出，而不是意识到这对于程序的功能至关重要。

更新：我不是说toString()不应该被覆盖，只是不是在这种特殊情况下，具体文本是必要的游戏。