net.jxta.impl.rendezvous.rpv.PeerViewSequentialStrategy Maven / Gradle / Ivy

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 * Copyright (c) 2002-2004 Sun Microsystems, Inc.  All rights reserved.
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 *     developed by Sun Microsystems, Inc. for JXTA(TM) technology." 
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package net.jxta.impl.rendezvous.rpv;

import java.util.SortedSet;
import java.util.Iterator;

/**
 * Sequential
 */
class PeerViewSequentialStrategy implements PeerViewStrategy {

    private final SortedSet set;
    private PeerViewElement current;

    PeerViewSequentialStrategy(SortedSet aset) {
        set = aset;
        reset();
    }

    /**
     * {@inheritDoc}
     */
    public void reset() {
        current = null;
    }

    /**
     * {@inheritDoc}
     */
    public PeerViewElement next() {

        synchronized (set) {
            do {
                if (null == current) {
                    if (!set.isEmpty()) {
                        // no current, take the first
                        current = (PeerViewElement) set.first();
                        break;
                    } else {
                        // no first, return null
                        break;
                    }
                } else {
                    SortedSet tail = set.tailSet(current);

                    Iterator fromTail = tail.iterator();

                    if (fromTail.hasNext()) {
                        PeerViewDestination tailFirst = fromTail.next();

                        if (0 == current.compareTo(tailFirst)) {
                            if (fromTail.hasNext()) {
                                // first in tail is current so the new current
                                // is second in tail.
                                current = (PeerViewElement) fromTail.next();
                                break;
                            } else {
                                // none left in tail after current, start over.
                                current = null;
                            }
                        } else {
                            // current is not in the tail set, so first in tail
                            // is new current
                            current = (PeerViewElement) tailFirst;
                            break;
                        }
                    } else {
                        // none in tail, start over.
                        current = null;
                    }
                }
                //FIXME by hamada this does not loop, current is always null, is the intended behavior?
            } while (null == current);
        }

        return current;
    }
}