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[SlowStrider]

I admit this is a little late (I found your exercise through google), but I think I have quite an elegant solution that is equivalent:

import static java.util.Arrays.asList;

import java.util.List;

import com.google.common.base.Joiner;

class UtilRefactored {

	public static CharSequence format(List<CharSequence> source) {
		return "Listing:\n" + addBrackets(Joiner.on("\n ").join(source));
	}

	public static CharSequence format(CharSequence... source) {
		return format(asList(source));
	}

	private static String addBrackets(String text) {
		String result = "[ " + text;
		if (!result.endsWith(" ") && (!result.endsWith("]"))) {
			result += " ";
		}
		return result + "]";
	}
}

If you don't wish to depend on Google guava, you can also replace "Joiner.on("\n ").join(source)" by a method call to join("\n ", source) with the following join method

	private static String join(String separator, CharSequence... source) {
		StringBuilder text = new StringBuilder();
		for (final CharSequence component : source) {
			text.append(component);
			text.append(separator);
		}
		if (text.length() == 0) {
			return "";
		}
		// Remove excess last separator
		return text.substring(0, text.length() - separator.length());
	}