java - 如何在 Java 中克隆具有最终字段的抽象对象？

Question

在this问题和这个post解释了如何使用 protected 复制构造函数克隆具有最终字段的对象。

但是，假设我们有:

public abstract class Person implements Cloneable
{
    private final Brain brain; // brain is final since I do not want 
                // any transplant on it once created!
    private int age;
    public Person(Brain aBrain, int theAge)
    {
        brain = aBrain; 
        age = theAge;
    }
    protected Person(Person another)
    {
        Brain refBrain = null;
        try
        {
            refBrain = (Brain) another.brain.clone();
            // You can set the brain in the constructor
        }
        catch(CloneNotSupportedException e) {}
        brain = refBrain;
        age = another.age;
    }
    public String toString()
    {
        return "This is person with " + brain;
        // Not meant to sound rude as it reads!
    }
    public Object clone()
    {
        return new Person(this);
    }

    public abstract void Think(); //!!!!
    …
}

返回一个错误，因为我们不能实例化一个抽象类。我们如何解决这个问题？

Answer 1

你不在抽象类中实现clone()方法，只在具体的子类中实现。

public class SomeConcretePerson extends Person
{
    public SomeConcretePerson (SomeConcretePerson another)
    {
        super (another); // this will invoke Person's copy constructor
    }

    public Object clone()
    {
        return new SomeConcretePerson(this);
    }
}