WeakList.java Source code

Introduction

Here is the source code for WeakList.java

Source

//Revised from objectweb jac

import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.AbstractList;
import java.util.ArrayList;
import java.util.List;

public class WeakList extends AbstractList {

    /**
     * Reference queue for cleared weak references
     */
    private final ReferenceQueue queue = new ReferenceQueue();

    private final List list = new ArrayList();

    public boolean add(Object o) {
        expungeStaleEntries();
        return list.add(new ListEntry(o, queue));
    }

    public Object get(int i) {
        expungeStaleEntries();
        return ((Reference) list.get(i)).get();
    }

    public int size() {
        //new Exception().printStackTrace();
        expungeStaleEntries();
        return list.size();
    }

    public Object remove(int index) {
        return ((ListEntry) list.remove(index)).get();
    }

    /**
     * Expunge stale entries from the list.
     */
    private void expungeStaleEntries() {
        Object r;
        while ((r = queue.poll()) != null) {
            ListEntry e = (ListEntry) r;
            int i = list.indexOf(r);
            if (i != -1) {
                list.remove(i);
            }
        }
    }

    private static class ListEntry extends WeakReference {
        String objectString;

        public ListEntry(Object o, ReferenceQueue queue) {
            super(o, queue);
            objectString = o.toString();
        }

        public boolean equals(Object o) {
            if (o == null) {
                return false;
            } else {
                if ((o instanceof ListEntry)) {
                    return o.hashCode() == this.hashCode();
                } else {
                    if (this.get() == null)
                        return false;
                    return this.get().equals(o);
                }
            }
        }

        public String toString() {
            if (this.get() == null) {
                return "'entry " + objectString + " <GARBAGED>'";
            } else {
                return "'entry " + this.get() + "'";
            }
        }

    }
}