Question

The following snippet from RuntimeUtil.java from jlibs guarantees GC that garbage collection is done.

Since, it also uses System.gc(), i dont understand how can they guarantee that it will happen 100% of the times.

Following is the snippet:

/**
     * This method guarantees that garbage collection is
     * done unlike <code>{@link System#gc()}</code>
     */
    public static void gc(){
        Object obj = new Object();
        WeakReference ref = new WeakReference<Object>(obj);
        obj = null;
        while(ref.get()!=null)
            System.gc();
    }

Answer 1

From what I can see it should work as they

1) create an object
2) get a “weak” reference to it
3) null the reference to it, in order to mark it for garbage collection
4) and wait with the while loop until it actually disappears