Java tutorial
/** * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ /** * <p>Operations on {@link java.lang.String} that are * <code>null</code> safe.</p> * * @see java.lang.String * @author <a href="http://jakarta.apache.org/turbine/">Apache Jakarta Turbine</a> * @author <a href="mailto:jon@latchkey.com">Jon S. Stevens</a> * @author Daniel L. Rall * @author <a href="mailto:gcoladonato@yahoo.com">Greg Coladonato</a> * @author <a href="mailto:ed@apache.org">Ed Korthof</a> * @author <a href="mailto:rand_mcneely@yahoo.com">Rand McNeely</a> * @author Stephen Colebourne * @author <a href="mailto:fredrik@westermarck.com">Fredrik Westermarck</a> * @author Holger Krauth * @author <a href="mailto:alex@purpletech.com">Alexander Day Chaffee</a> * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a> * @author Arun Mammen Thomas * @author Gary Gregory * @author Phil Steitz * @author Al Chou * @author Michael Davey * @author Reuben Sivan * @author Chris Hyzer * @author Scott Johnson * @since 1.0 * @version $Id: StringUtils.java 635447 2008-03-10 06:27:09Z bayard $ */ public class Main { // StripAll //----------------------------------------------------------------------- /** * <p>Strips whitespace from the start and end of every String in an array. * Whitespace is defined by {@link Character#isWhitespace(char)}.</p> * * <p>A new array is returned each time, except for length zero. * A <code>null</code> array will return <code>null</code>. * An empty array will return itself. * A <code>null</code> array entry will be ignored.</p> * * <pre> * StringUtils.stripAll(null) = null * StringUtils.stripAll([]) = [] * StringUtils.stripAll(["abc", " abc"]) = ["abc", "abc"] * StringUtils.stripAll(["abc ", null]) = ["abc", null] * </pre> * * @param strs the array to remove whitespace from, may be null * @return the stripped Strings, <code>null</code> if null array input */ public static String[] stripAll(String[] strs) { return stripAll(strs, null); } /** * <p>Strips any of a set of characters from the start and end of every * String in an array.</p> * Whitespace is defined by {@link Character#isWhitespace(char)}.</p> * * <p>A new array is returned each time, except for length zero. * A <code>null</code> array will return <code>null</code>. * An empty array will return itself. * A <code>null</code> array entry will be ignored. * A <code>null</code> stripChars will strip whitespace as defined by * {@link Character#isWhitespace(char)}.</p> * * <pre> * StringUtils.stripAll(null, *) = null * StringUtils.stripAll([], *) = [] * StringUtils.stripAll(["abc", " abc"], null) = ["abc", "abc"] * StringUtils.stripAll(["abc ", null], null) = ["abc", null] * StringUtils.stripAll(["abc ", null], "yz") = ["abc ", null] * StringUtils.stripAll(["yabcz", null], "yz") = ["abc", null] * </pre> * * @param strs the array to remove characters from, may be null * @param stripChars the characters to remove, null treated as whitespace * @return the stripped Strings, <code>null</code> if null array input */ public static String[] stripAll(String[] strs, String stripChars) { int strsLen; if (strs == null || (strsLen = strs.length) == 0) { return strs; } String[] newArr = new String[strsLen]; for (int i = 0; i < strsLen; i++) { newArr[i] = strip(strs[i], stripChars); } return newArr; } /** * <p>Strips any of a set of characters from the start and end of a String. * This is similar to {@link String#trim()} but allows the characters * to be stripped to be controlled.</p> * * <p>A <code>null</code> input String returns <code>null</code>. * An empty string ("") input returns the empty string.</p> * * <p>If the stripChars String is <code>null</code>, whitespace is * stripped as defined by {@link Character#isWhitespace(char)}. * Alternatively use {@link #strip(String)}.</p> * * <pre> * StringUtils.strip(null, *) = null * StringUtils.strip("", *) = "" * StringUtils.strip("abc", null) = "abc" * StringUtils.strip(" abc", null) = "abc" * StringUtils.strip("abc ", null) = "abc" * StringUtils.strip(" abc ", null) = "abc" * StringUtils.strip(" abcyx", "xyz") = " abc" * </pre> * * @param str the String to remove characters from, may be null * @param stripChars the characters to remove, null treated as whitespace * @return the stripped String, <code>null</code> if null String input */ public static String strip(String str, String stripChars) { if (isEmpty(str)) { return str; } str = stripStart(str, stripChars); return stripEnd(str, stripChars); } /** * <p>Strips any of a set of characters from the start of a String.</p> * * <p>A <code>null</code> input String returns <code>null</code>. * An empty string ("") input returns the empty string.</p> * * <p>If the stripChars String is <code>null</code>, whitespace is * stripped as defined by {@link Character#isWhitespace(char)}.</p> * * <pre> * StringUtils.stripStart(null, *) = null * StringUtils.stripStart("", *) = "" * StringUtils.stripStart("abc", "") = "abc" * StringUtils.stripStart("abc", null) = "abc" * StringUtils.stripStart(" abc", null) = "abc" * StringUtils.stripStart("abc ", null) = "abc " * StringUtils.stripStart(" abc ", null) = "abc " * StringUtils.stripStart("yxabc ", "xyz") = "abc " * </pre> * * @param str the String to remove characters from, may be null * @param stripChars the characters to remove, null treated as whitespace * @return the stripped String, <code>null</code> if null String input */ public static String stripStart(String str, String stripChars) { int strLen; if (str == null || (strLen = str.length()) == 0) { return str; } int start = 0; if (stripChars == null) { while ((start != strLen) && Character.isWhitespace(str.charAt(start))) { start++; } } else if (stripChars.length() == 0) { return str; } else { while ((start != strLen) && (stripChars.indexOf(str.charAt(start)) != -1)) { start++; } } return str.substring(start); } /** * <p>Strips any of a set of characters from the end of a String.</p> * * <p>A <code>null</code> input String returns <code>null</code>. * An empty string ("") input returns the empty string.</p> * * <p>If the stripChars String is <code>null</code>, whitespace is * stripped as defined by {@link Character#isWhitespace(char)}.</p> * * <pre> * StringUtils.stripEnd(null, *) = null * StringUtils.stripEnd("", *) = "" * StringUtils.stripEnd("abc", "") = "abc" * StringUtils.stripEnd("abc", null) = "abc" * StringUtils.stripEnd(" abc", null) = " abc" * StringUtils.stripEnd("abc ", null) = "abc" * StringUtils.stripEnd(" abc ", null) = " abc" * StringUtils.stripEnd(" abcyx", "xyz") = " abc" * </pre> * * @param str the String to remove characters from, may be null * @param stripChars the characters to remove, null treated as whitespace * @return the stripped String, <code>null</code> if null String input */ public static String stripEnd(String str, String stripChars) { int end; if (str == null || (end = str.length()) == 0) { return str; } if (stripChars == null) { while ((end != 0) && Character.isWhitespace(str.charAt(end - 1))) { end--; } } else if (stripChars.length() == 0) { return str; } else { while ((end != 0) && (stripChars.indexOf(str.charAt(end - 1)) != -1)) { end--; } } return str.substring(0, end); } // Empty checks //----------------------------------------------------------------------- /** * <p>Checks if a String is empty ("") or null.</p> * * <pre> * StringUtils.isEmpty(null) = true * StringUtils.isEmpty("") = true * StringUtils.isEmpty(" ") = false * StringUtils.isEmpty("bob") = false * StringUtils.isEmpty(" bob ") = false * </pre> * * <p>NOTE: This method changed in Lang version 2.0. * It no longer trims the String. * That functionality is available in isBlank().</p> * * @param str the String to check, may be null * @return <code>true</code> if the String is empty or null */ public static boolean isEmpty(String str) { return str == null || str.length() == 0; } }