CollectionUtils 判断空 和 join分隔符

package cn.trinea.android.common.util;import java.util.Collection;import android.text.TextUtils;/** * CollectionUtils *  * @author <a href="http://www.trinea.cn" target="_blank">Trinea</a> 2012-7-22 */public class CollectionUtils {    /** default join separator **/    public static final CharSequence DEFAULT_JOIN_SEPARATOR = ",";    private CollectionUtils() {        throw new AssertionError();    }    /**     * is null or its size is 0     *      * <pre>     * isEmpty(null)   =   true;     * isEmpty({})     =   true;     * isEmpty({1})    =   false;     * </pre>     *      * @param <V>     * @param c     * @return if collection is null or its size is 0, return true, else return false.     */    public static <V> boolean isEmpty(Collection<V> c) {        return (c == null || c.size() == 0);    }    /**     * join collection to string, separator is {@link #DEFAULT_JOIN_SEPARATOR}     *      * <pre>     * join(null)      =   "";     * join({})        =   "";     * join({a,b})     =   "a,b";     * </pre>     *      * @param collection     * @return join collection to string, separator is {@link #DEFAULT_JOIN_SEPARATOR}. if collection is empty, return     *         ""     */    public static String join(Iterable collection) {        return collection == null ? "" : TextUtils.join(DEFAULT_JOIN_SEPARATOR, collection);    }}