Example usage for java.lang.ref ReferenceQueue poll

Introduction

In this page you can find the example usage for java.lang.ref ReferenceQueue poll.

Prototype

public Reference<? extends T> poll() 

Source Link

Document

Polls this queue to see if a reference object is available.

Usage

From source file:WeakCanonicalSet.java

/**
 * Pass in a candidate canonical object and get a unique instance from this
 * set. The returned object will always be of the same type as that passed
 * in. If the object passed in does not equal any object currently in the
 * set, it will be added to the set, becoming canonical.
 *
 * @param obj candidate canonical object; null is also accepted
 *///  w  ww .jav  a  2s  .  co m
public synchronized <U extends T> U put(U obj) {
    // This implementation is based on the WeakIdentityMap.put method.

    if (obj == null) {
        return null;
    }

    Entry<T>[] tab = this.table;

    // Cleanup after cleared References.
    {
        ReferenceQueue queue = this.queue;
        Reference ref;
        while ((ref = queue.poll()) != null) {
            // Since buckets are single-linked, traverse entire list and
            // cleanup all cleared references in it.
            int index = (((Entry) ref).hash & 0x7fffffff) % tab.length;
            for (Entry<T> e = tab[index], prev = null; e != null; e = e.next) {
                if (e.get() == null) {
                    if (prev != null) {
                        prev.next = e.next;
                    } else {
                        tab[index] = e.next;
                    }
                    this.count--;
                } else {
                    prev = e;
                }
            }
        }
    }

    int hash = hashCode(obj);
    int index = (hash & 0x7fffffff) % tab.length;

    for (Entry<T> e = tab[index], prev = null; e != null; e = e.next) {
        T iobj = e.get();
        if (iobj == null) {
            // Clean up after a cleared Reference.
            if (prev != null) {
                prev.next = e.next;
            } else {
                tab[index] = e.next;
            }
            this.count--;
        } else if (e.hash == hash && obj.getClass() == iobj.getClass() && equals(obj, iobj)) {
            // Found canonical instance.
            return (U) iobj;
        } else {
            prev = e;
        }
    }

    if (this.count >= this.threshold) {
        // Rehash the table if the threshold is exceeded.
        rehash();
        tab = this.table;
        index = (hash & 0x7fffffff) % tab.length;
    }

    // Create a new entry.
    tab[index] = new Entry<T>(obj, this.queue, hash, tab[index]);
    this.count++;
    return obj;
}

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From source file:WeakIdentityMap.java

private void cleanup() {
    // Cleanup after cleared References.
    Entry[] tab = this.table;
    ReferenceQueue queue = this.queue;
    Reference ref;//from w w  w  . j a  v  a2s  . com
    while ((ref = queue.poll()) != null) {
        // Since buckets are single-linked, traverse entire list and
        // cleanup all cleared references in it.
        int index = (((Entry) ref).hash & 0x7fffffff) % tab.length;
        for (Entry e = tab[index], prev = null; e != null; e = e.next) {
            if (e.get() == null) {
                this.modCount++;
                if (prev != null) {
                    prev.next = e.next;
                } else {
                    tab[index] = e.next;
                }
                this.count--;
            } else {
                prev = e;
            }
        }
    }
}

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