Improved version of Apache's StringUtils

StringUtils.java

/**
 * @author quydm
 */
public class StringUtils {

    public static final String EMPTY_STRING = "";

    public static String join(Object[] array, String separator) {
        return join(array, separator, 0, array.length);
    }

    public static String join(Object[] array, String separator, int startIndex, int endIndex) {
        if (array == null) {
            return null;
        }
        int noOfItems = endIndex - startIndex;
        if (noOfItems <= 0) {
            return EMPTY_STRING;
        }
        if (noOfItems == 1) {
            return String.valueOf(array[startIndex]);
        }
        int newEndIndex = endIndex - 1;
        final StringBuilder buf = new StringBuilder();
        for (int i = startIndex; i < newEndIndex; i++) {
            buf.append(array[i]).append(separator);
        }
        buf.append(array[newEndIndex]);
        return buf.toString();
    }

}