Adding hash tag charactor to a string (adding #)

HashTagBuilder.java

import java.util.List;

/**
 * Adds the # character to all words of the text.
 * 
 * @author https://github.com/jurigis
 */
public class HashTagBuilder {

	public static String addHashTags(final String textToTag, final List<String> wordList) {
		// If the list of words is empty we return the text as it is.
		if (wordList == null || wordList.isEmpty()) {
			return textToTag;
		}
		final StringBuilder sb = new StringBuilder(textToTag);
		wordList.stream().filter(word -> (word != null && !word.isEmpty())).forEach(word -> {
			int currentPos = 0;
			while (currentPos >= 0) {
				currentPos = sb.toString().toLowerCase().indexOf(word.toLowerCase(), currentPos);
				if (currentPos > 0) {
					sb.insert(currentPos, '#');
					currentPos += 2;
				}
			}
		});
		return sb.toString();
	}
}