java 取消引用_java编译时所说的“无法取消引用”是什么意思

部分代码如下：publicabstractclassAnimal//animal类定义为抽象类{publicstaticfinalbooleanisMammal=false;publicstaticfinalbooleanisCarnivorous=false;publicabstractvoidsetMood...

部分代码如下：

public abstract class Animal //animal类定义为抽象类

{

public static final boolean isMammal=false;

public static final boolean isCarnivorous=false;

public abstract void setMood(int newMood);

public abstract int getMood();

public static final int SCARE=0;

public static final int COMFORTED=1;

public static final int USUAL=2;

public static final int mood=COMFORTED;

public abstract String sayHello(int nowMood);

}

class Frog extends Animal implements WaterAnimal

{

protected boolean isMammal;

protected boolean isCarnivorous;

protected int mood;

public Frog(){

isMammal=false;

isCarnivorous=false;

mood=0;

}

public void setMood(int newMood){

mood=newMood;

}

public int getMood(){

return mood;

}

public String sayHello(int nowMood){

this.setMood(nowMood);

if(mood.equals(Animal.COMFORTED))

return ("呱呱呱");

else if(mood.equals(Animal.SCARE))

return ("扑通一声跳入水中");

else

return ("一动不动");

}

}

在编译时总是提示if(mood.equals(Animal.COMFORTED))这一句中无法取消引用。有哪位人士知道其中原因吗？？

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