jodd-core/src/main/java/jodd/util/StringUtil.java
public static String join(final Object[] array, final String separator) {
		if (array == null) {
			return null;
		}

		if (array.length == 0) {
			return StringPool.EMPTY;
		}

		if (array.length == 1) {
			return String.valueOf(array[0]);
		}

		final StringBuilder sb = new StringBuilder(array.length * 16);

		for (int i = 0; i < array.length; i++) {

			if (i > 0) {
				sb.append(separator);
			}

			sb.append(array[i]);
		}

		return sb.toString();
	}
public static String join(final Object[] array, final String separator) {
		if (array == null) {
			return null;
		}

		if (array.length == 0) {
			return StringPool.EMPTY;
		}

		if (array.length == 1) {
			return String.valueOf(array[0]);
		}

		final StringBuilder sb = new StringBuilder(array.length * 16);

		for (int i = 0; i < array.length; i++) {

			if (i > 0) {
				sb.append(separator);
			}

			sb.append(array[i]);
		}

		return sb.toString();
	}
Joins an array of objects into one string with separator.