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jsync.io is a non-blocking, event-driven networking framework for Java

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/*
 * Copyright (c) 2011-2013 The original author or authors
 * ------------------------------------------------------
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Apache License v2.0 which accompanies this distribution.
 *
 *     The Eclipse Public License is available at
 *     http://www.eclipse.org/legal/epl-v10.html
 *
 *     The Apache License v2.0 is available at
 *     http://www.opensource.org/licenses/apache2.0.php
 *
 * You may elect to redistribute this code under either of these licenses.
 */

package io.jsync.spi.cluster.impl;

import io.jsync.impl.ConcurrentHashSet;
import io.jsync.spi.cluster.ChoosableIterable;

import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Set;

/**
 * @author Tim Fox
 */
public class ChoosableSet implements ChoosableIterable {

    private final Set ids;
    private volatile boolean initialised;
    private volatile Iterator iter;

    public ChoosableSet(int initialSize) {
        ids = new ConcurrentHashSet<>(initialSize);
    }

    public int size() {
        return ids.size();
    }

    public boolean isInitialised() {
        return initialised;
    }

    public void setInitialised() {
        this.initialised = true;
    }

    public void add(T elem) {
        ids.add(elem);
    }

    public void remove(T elem) {
        ids.remove(elem);
    }

    public void merge(ChoosableSet toMerge) {
        ids.addAll(toMerge.ids);
    }

    public boolean isEmpty() {
        return ids.isEmpty();
    }

    @Override
    public Iterator iterator() {
        return ids.iterator();
    }

    public synchronized T choose() {
        if (!ids.isEmpty()) {
            if (iter == null || !iter.hasNext()) {
                iter = ids.iterator();
            }
            try {
                return iter.next();
            } catch (NoSuchElementException e) {
                return null;
            }
        } else {
            return null;
        }
    }
}