克隆一个实例化的抽象类 [英] Cloning an instantiated abstract class

问题描述

实例化一个抽象类.-> 复制它，保留抽象方法的实现.

    public abstract class Foo{… 

    public int myVar;

    public abstract void do();

     }//Foo

包中的其他地方:

public class Gha{ … 

    Foo testFoo = new Foo{

        @Override
        public void do(){
            Log.i("" , "this is a special Foo"); //executable process
        }//do

    }//testFoo
    …
}//Gha

我可以以复制 testFoo 的 .do() 方法主体的方式复制 testFoo 以用于新的 Foo?

Can I copy testFoo in a way that copies testFoo’s .do() method body for the new Foo?

推荐答案

您可以使用 clone.普遍不鼓励使用这种方法，但它确实有效.

You could use clone. The use of this method is widely discouraged, but it does work.

例如:

public abstract class Foo implements Cloneable {

    private int a;
    private String b;

    public Foo(int a, String b) {
        this.a = a;
        this.b = b;
    } 

    public abstract void run();

    public int getA() { return a; }

    public String getB() { return b; }

    @Override
    public final Foo clone() {
        try {
            return (Foo) super.clone();
        } catch (CloneNotSupportedException e) {
            throw new AssertionError(); // Can't happen
        }
    }
}

然后，你可以这样做:

Foo original = new Foo(3, "bar") {
    @Override
    public void run() {
        System.out.println("Hello, world!");
    }
};
Foo copy = original.clone();
System.out.println(copy.getA());
System.out.println(copy.getB());
copy.run();
System.out.println(copy == original);

输出为:

3
bar
Hello, world!
false

另一种方法是使用 Serializable.

public abstract class Foo implements Serializable {

    private int a;
    private String b;

    public Foo(int a, String b) {
        this.a = a;
        this.b = b;
    }

    public abstract void run();

    public int getA() { return a; }

    public String getB() { return b; }

    public final Foo copy() {
        try {
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            new ObjectOutputStream(baos).writeObject(this);
            return (Foo) new ObjectInputStream(new ByteArrayInputStream(baos.toByteArray())).readObject();
        } catch (Exception e) {
            throw new AssertionError(); 
        }
    }
}

在此版本中，将 clone 替换为 copy，您将得到相同的结果.

With this version, replace clone by copy and you'll get the same result.

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