Useful String utilities
/* * net/balusc/util/StringUtil.java * * Copyright (C) 2007 BalusC * * This program is free software; you can redistribute it and/or modify it under the terms of the * GNU General Public License as published by the Free Software Foundation; either version 2 of the * License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without * even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * * You should have received a copy of the GNU General Public License along with this program; if * not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA * 02110-1301, USA. */ package net.balusc.util; import java.util.Collection; import java.util.Iterator; /** * Useful String utilities. * * @author BalusC * @link http://balusc.blogspot.com/2006/10/stringutil.html */ public final class StringUtil { // Init --------------------------------------------------------------------------------------- /** Argument for <tt>StringUtil#pad()</tt>, set the pad direction to LEFT. */ public static final int PAD_LEFT = -1; /** Argument for <tt>StringUtil#pad()</tt>, set the pad direction to BOTH. */ public static final int PAD_BOTH = 0; /** Argument for <tt>StringUtil#pad()</tt>, set the pad direction to RIGHT. */ public static final int PAD_RIGHT = 1; private StringUtil() { // Utility class, hide the constructor. } // Actions ------------------------------------------------------------------------------------ /** * Pad the given string with the given pad value to the given length in the given direction. * Valid directions are <tt>StringUtil.PAD_LEFT</tt>, <tt>StringUtil.PAD_BOTH</tt> and * <tt>StringUtil.PAD_RIGHT</tt>. When using <tt>StringUtil.PAD_BOTH</tt>, padding left * has precedence over padding right when difference between string's length and the given * length is odd. * @param string The string to be padded. * @param pad The value to pad the given string with. * @param length The length to pad the given string to. * @param direction The direction to pad the given string to. * @return The padded string. * @throws IllegalArgumentException If invalid direction is given. */ public static String pad(String string, String pad, int length, int direction) throws IllegalArgumentException { StringBuilder builder = new StringBuilder(string); switch (direction) { case PAD_LEFT: while (builder.length() < length) { builder.insert(0, pad); } break; case PAD_RIGHT: while (builder.length() < length) { builder.append(pad); } break; case PAD_BOTH: int right = (length - builder.length()) / 2 + builder.length(); while (builder.length() < right) { builder.append(pad); } while (builder.length() < length) { builder.insert(0, pad); } break; default: throw new IllegalArgumentException("Invalid direction, must be one of" + " StringUtil.PAD_LEFT, StringUtil.PAD_BOTH or StringUtil.PAD_RIGHT."); } return builder.toString(); } /** * Trim the given string with the given trim value. * @param string The string to be trimmed. * @param trim The value to trim the given string off. * @return The trimmed string. */ public static String trim(String string, String trim) { if (trim.length() == 0) { return string; } int start = 0; int end = string.length(); int length = trim.length(); while (start + length <= end && string.substring(start, start + length).equals(trim)) { start += length; } while (start + length <= end && string.substring(end - length, end).equals(trim)) { end -= length; } return string.substring(start, end); } /** * Join the given collection with the given join value. * @param collection The collection (List, Set) to be joined. * @param join The value to be joined between each part. * @return The joined collection. */ public static String join(Collection<?> collection, String join) { StringBuilder builder = new StringBuilder(); for (Iterator<?> iter = collection.iterator(); iter.hasNext();) { builder.append(iter.next()); if (iter.hasNext()) { builder.append(join); } } return builder.toString(); } /** * Join the given ordinary array with the given join value. * @param objects The ordinary array (String[], Integer[], etc) to be joined. * @param join The value to be joined between each part. * @return The joined array. */ public static String join(Object[] objects, String join) { StringBuilder builder = new StringBuilder(); for (int i = 0; i < objects.length;) { builder.append(objects[i]); if (++i < objects.length) { builder.append(join); } } return builder.toString(); } /** * Decapitalize the given string. The first character will be lowercased. * @param string The string to decapitalize. * @return The decapitalized string. */ public static String decapitalize(String string) { if (string.length() == 0) { return string; } return string.substring(0, 1).toLowerCase() + string.substring(1); } /** * Check if given string is a number. It should contain digits only. * @param string The string to check on. * @return True if string is a number. False if not. */ public static boolean isNumber(String string) { return string.matches("^\\d+$"); } /** * Check if given string is numeric. Positive and negative prefix and dot separators are * allowed. * @param string The string to check on. * @return True if string is numeric. False if not. */ public static boolean isNumeric(String string) { return string.matches("^[-+]?\\d+(\\.\\d+)?$"); } /** * Check if given string is a valuta. The dot separator and two decimals are required. * @param string The string to check on. * @return True if string is valuta. False if not. */ public static boolean isValuta(String string) { return string.matches("^\\d+\\.\\d{2}$"); } /** * Check if given string contains numbers. * @param string The string to check on. * @return True if string contains numbers. False if not. */ public static boolean hasNumbers(String string) { return string.matches("^.*\\d.*$"); } /** * Check if given string is a valid email address. This confirms the RFC822 & RFC1035 * specifications. * @param string The string to check on. * @return True if string is an valid email address. False if not. */ public static boolean isEmailAddress(String string) { return string.toLowerCase().matches( "^[a-z0-9-~#&\\_]+(\\.[a-z0-9-~#&\\_]+)*@([a-z0-9-]+\\.)+[a-z]{2,5}$"); } /** * Remove any XSS (Cross Site Scripting) vulrenabilities from the given string. * @param string The string to remove XSS from. * @return The string with removed XSS, if any. */ public static String removeXss(String string) { return string .replaceAll("(?i)<script.*?>.*?</script.*?>", "") // Remove all <script> tags. .replaceAll("(?i)<.*?javascript:.*?>.*?</.*?>", "") // Remove tags with javascript: call. .replaceAll("(?i)<.*?\\s+on.*?>.*?</.*?>", ""); // Remove tags with on* attributes. } }
Instead of using regexps for isNumber and isNumeric, you can also consider the following implementations (mis)using the NumberFormatException:
/**
* Check if given string is a number. It should contain digits only.
* @param string The string to check on.
* @return True if string is a number. False if not.
*/
public static boolean isNumber(String string) {
try {
new BigInteger(string);
return true;
} catch (NumberFormatException e) {
return false;
}
}
/**
* Check if given string is numeric. Positive and negative prefix
* and dot separators are allowed.
* @param string The string to check on.
* @return True if string is numeric. False if not.
*/
public static boolean isNumeric(String string) {
try {
new BigDecimal(string);
return true;
} catch (NumberFormatException e) {
return false;
}
}
In perspective to the regexp methods, those methods are slightly faster (about 10%) when no exception is thrown, but those are much more slower (about 5 times slower) when an exception will be thrown.
Copyright - GNU General Public License
(C) October 2006, BalusC
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