您无法执行此操作,因为在比较父类时,编译器无法确定子类会对其进行初始化。您必须在父级的构造函数中对其进行初始化,然后让子级调用父级的构造函数:
public abstract class Parent { protected final String birthmark; protected Parent(String s) { birthmark = s; }}public class Child extends Parent { public Child(String s) { super(s); ... }}


