java - 为什么这个枚举不能编译？

Question

为什么这个枚举无法编译？

public enum Ackr implements Cloneable{
    INSTANCE;

    public <Ackr extends Cloneable> Ackr getInstance(){
        return INSTANCE; //Type mismatch: cannot convert from Ackr to Ackr
//      return (Ackr)INSTANCE; //Type safety: Unchecked cast from Ackr to Ackr
    }
}

Answer 1

据我所知，该类型参数是不必要的。简单尝试一下

public Ackr getInstance(){
    return INSTANCE;
}