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package oracle.toplink.essentials.internal.identitymaps;

import java.util.*;

/**
 * Used to allow iterating over a maps cache keys.
 */
public class IdentityMapKeyEnumeration implements Enumeration {
    protected FullIdentityMap map;
    protected Enumeration cacheKeysEnum;
    protected CacheKey nextKey;

    public IdentityMapKeyEnumeration(FullIdentityMap map) {
        this.map = map;
        this.cacheKeysEnum = map.getCacheKeys().elements();
    }

    public boolean hasMoreElements() {
        this.nextKey = getNextCacheKey();
        return this.nextKey != null;
    }

    public Object nextElement() {
        if (this.nextKey == null) {
            throw new NoSuchElementException("IdentityMapKeyEnumeration nextElement");
        }

        // CR#... Must check the read lock to avoid
        // returning half built objects.
        this.nextKey.checkReadLock();
        return this.nextKey;
    }

    protected CacheKey getNextCacheKey() {
        CacheKey key = null;
        while (cacheKeysEnum.hasMoreElements() && (key == null)) {
            key = (CacheKey)cacheKeysEnum.nextElement();
        }
        return key;
    }
}