StringUtil.java

package org.bukkit.util;

import java.util.Collection;

import org.apache.commons.lang3.Validate;

public class StringUtil {

	/**
	 * Copies all elements from the iterable collection of originals to the
	 * collection provided.
	 * 
	 * @param token
	 *            String to search for
	 * @param originals
	 *            An iterable collection of strings to filter.
	 * @param collection
	 *            The collection to add matches to
	 * @return the collection provided that would have the elements copied into
	 * @throws UnsupportedOperationException
	 *             if the collection is immutable and originals contains a
	 *             string which starts with the specified search string.
	 * @throws IllegalArgumentException
	 *             if any parameter is is null
	 * @throws IllegalArgumentException
	 *             if originals contains a null element. <b>Note: the collection
	 *             may be modified before this is thrown</b>
	 */
	public static <T extends Collection<String>> T copyPartialMatches(final String token, final Iterable<String> originals, final T collection) throws UnsupportedOperationException, IllegalArgumentException {
		Validate.notNull(token, "Search token cannot be null");
		Validate.notNull(collection, "Collection cannot be null");
		Validate.notNull(originals, "Originals cannot be null");

		for (String string : originals) {
			if (startsWithIgnoreCase(string, token)) {
				collection.add(string);
			}
		}

		return collection;
	}

	/**
	 * This method uses a substring to check case-insensitive equality. This
	 * means the internal array does not need to be copied like a toLowerCase()
	 * call would.
	 * 
	 * @param string
	 *            String to check
	 * @param prefix
	 *            Prefix of string to compare
	 * @return true if provided string starts with, ignoring case, the prefix
	 *         provided
	 * @throws NullPointerException
	 *             if prefix is null
	 * @throws IllegalArgumentException
	 *             if string is null
	 */
	public static boolean startsWithIgnoreCase(final String string, final String prefix) throws IllegalArgumentException, NullPointerException {
		Validate.notNull(string, "Cannot check a null string for a match");
		if (string.length() < prefix.length()) {
			return false;
		}
		return string.substring(0, prefix.length()).equalsIgnoreCase(prefix);
	}
}