Thinking in Java(8)-inheritance and cleanup

最新推荐文章于 2021-02-27 14:36:42 发布

超超级钢铁侠

最新推荐文章于 2021-02-27 14:36:42 发布

阅读量416

点赞数 1

CC 4.0 BY-SA版权

分类专栏： Java核心-基础文章标签： java 对象继承 class

本文链接：https://blog.youkuaiyun.com/qq_23851075/article/details/53641868

Java核心-基础专栏收录该内容

40 篇文章

订阅专栏

本文通过一个Java示例程序介绍了如何使用引用计数来跟踪对象的初始化和清理过程。示例展示了Shared类和Composing类之间的引用传递，并演示了在不同情况下对象的创建与销毁顺序。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

大家都知道，在继承中，不共享变量时，Java类对象initialize的顺序和cleanup的顺序相反，但是共享变量时情况就比较复杂了，这时使用一个final变量跟踪引用是一个好方法，可以清楚地看到对象的initialize和cleanup情况:

class Shared{
    private int refcount = 0;
    private static long counter = 0;
    private final long id = counter++;
    public Shared ()
    {
        System.out.println(" Creating" + this);
    }

    public void addRef()
    {
        refcount++;
    }

    protected void dispose()
    {
        if (--refcount == 0)
            System.out.println("Disposing " + this);
    }

    public String toString()
    {
        return ("Shared " + id);
    }

    protected void finalize() {
        if(refcount != 0)
            System.out.println("Error: object is not properly cleaned-up!");
}
}

class Composing{
    private Shared shared;
    private static long counter = 0;
    private final long id = counter++;
    public Composing(Shared shared)
    {
        System.out.println("Creating " + this);
        this.shared = shared;
        this.shared.addRef();
    }

    protected void dispose()
    {
        System.out.println("disposing " + this);
        shared.dispose();

    }

    public String toString()
    {
        return ("Composing " + id );
    }
}


public class ReferenceCounting {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Shared shared = new Shared();
        Composing[] composing = {new Composing(shared),new Composing(shared),new Composing(shared),new Composing(shared)
                ,new Composing(shared)};
        for (Composing c : composing)
            c.dispose();
        System.gc();
        // Verify failure:
        new Composing(new Shared());
        System.gc();

    }

}