我需要在Java中克隆一个子类,但是在代码中发生这种情况的那一点上,我将不知道子类的类型,只知道父类(super class)。最佳的设计模式是什么?

例子:

class Foo {
    String myFoo;
    public Foo(){}
    public Foo(Foo old) {
        this.myFoo = old.myFoo;
    }
}

class Bar extends Foo {
    String myBar;
    public Bar(){}
    public Bar(Bar old) {
        super(old); // copies myFoo
        this.myBar = old.myBar;
    }
}

class Copier {
    Foo foo;

    public Foo makeCopy(Foo oldFoo) {

        // this doesn't work if oldFoo is actually an
        // instance of Bar, because myBar is not copied
        Foo newFoo = new Foo(oldFoo);
        return newFoo;

        // unfortunately, I can't predict what oldFoo's the actual class
        // is, so I can't go:
        // if (oldFoo instanceof Bar) { // copy Bar here }
    }
}

最佳答案

如果您可以控制要复制的类,则可以使用虚拟方法:

class Foo {
    ...
    public Foo copy() {
        return new Foo(this);
    }
}
class Bar extends Foo {
    ...
    @Override public Bar copy() {
        return new Bar(this);
    }
}

(理想情况下,使类成为抽象类或使类最终成为类。)

关于java - 克隆Java中的子类,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/4329141/

10-11 23:04
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