无论如何，实例变量都设置为null

Question

所以我试图创建一个对象＆＃34; Cat＆＃34;它有名字，重量和心情。将Cat值分配给这些变量后，它仅打印名称和重量，而不是心情。它会说：＆＃34;姓名：猫，体重：10磅，心情：无效＆＃34;，无论情绪是否有效。

我认为这可能是变异器的一个问题，但我找不到任何可以修复它的东西。为了更进一步，该类的属性继承了这个＆＃34; Cat＆＃34; class也有这个问题，但它的新属性不是，所以它看起来像＆＃34;名称：猫，体重：10磅，心情：null，类型：短发＆＃34;。为什么会这样？

public class Cat extends Animal{

//Attributes
private String mood;

//Constructors
public Cat()
{
    super();
    this.mood = "no mood yet";
}
public Cat(String aName, double aWeight, String aMood)
{
    super(aName, aWeight);
    this.setMood(aMood);
}

//Accessors
public String getMood()
{
    return this.mood;
}

//Mutators
public void setMood(String aMood)
{
    if(aMood.equalsIgnoreCase("sleepy") || aMood.equalsIgnoreCase("playful") || aMood.equalsIgnoreCase("hungry"))
    {
        this.mood = aMood;
    }
    else
    {
        System.out.println("Invalid mood.");
    }
}

//Other Methods
public String toString()
{
    return super.toString() + " | Mood: " + this.mood;
}


public class Animal {

//Attributes
private String name;
private double weight;

//Constructors
public Animal()
{
    this.name = "no name yet";
    this.weight = 0.0;
}
public Animal(String aName, double aWeight)
{
    this.setName(aName);
    this.setWeight(aWeight);
}

//Accessors
public String getName()
{
    return this.name;
}
public double getWeight()
{
    return this.weight;
}

//Mutators
public void setName(String aName)
{
    this.name = aName;
}
public void setWeight(double aWeight)
{
    if (aWeight > 0.0)
    {
        this.weight = aWeight;
    }
    else
    {
        System.out.println("Invalid weight.");
    }
}