} else if (o instanceof java.util.Date) {
            if (pattern != null) {
                return new BigDecimal(new SimpleDateFormat(pattern).format(o));
            }
            return new BigDecimal(Long.toString(((java.util.Date) o).getTime()));
        } else if (o instanceof String) {
            final String s = (String) o;
            if (StringUtil.isEmpty(s)) {
                return null;
            }

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

/**
 * @author shinsuke
 *
 */
public class LruHashSet<E> extends AbstractSet<E> implements Set<E>, java.io.Serializable {
    private static final long serialVersionUID = 1L;

    private final LruHashMap<E, Object> map;

    // Dummy value to associate with an Object in the backing Map
    private static final Object PRESENT = new Object();