Java tutorial
/* * Copyright 2002-2019 the original author or authors. * * Licensed 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 * * https://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. */ package org.springframework.util; import java.io.ByteArrayOutputStream; import java.nio.charset.Charset; import java.util.ArrayList; import java.util.Arrays; import java.util.Collection; import java.util.Collections; import java.util.Enumeration; import java.util.Iterator; import java.util.LinkedHashSet; import java.util.LinkedList; import java.util.List; import java.util.Locale; import java.util.Properties; import java.util.Set; import java.util.StringJoiner; import java.util.StringTokenizer; import java.util.TimeZone; import org.springframework.lang.Nullable; /** * Miscellaneous {@link String} utility methods. * * <p>Mainly for internal use within the framework; consider * <a href="https://commons.apache.org/proper/commons-lang/">Apache's Commons Lang</a> * for a more comprehensive suite of {@code String} utilities. * * <p>This class delivers some simple functionality that should really be * provided by the core Java {@link String} and {@link StringBuilder} * classes. It also provides easy-to-use methods to convert between * delimited strings, such as CSV strings, and collections and arrays. * * @author Rod Johnson * @author Juergen Hoeller * @author Keith Donald * @author Rob Harrop * @author Rick Evans * @author Arjen Poutsma * @author Sam Brannen * @author Brian Clozel * @since 16 April 2001 */ public abstract class StringUtils { private static final String[] EMPTY_STRING_ARRAY = {}; private static final String FOLDER_SEPARATOR = "/"; private static final String WINDOWS_FOLDER_SEPARATOR = "\\"; private static final String TOP_PATH = ".."; private static final String CURRENT_PATH = "."; private static final char EXTENSION_SEPARATOR = '.'; //--------------------------------------------------------------------- // General convenience methods for working with Strings //--------------------------------------------------------------------- /** * Check whether the given object (possibly a {@code String}) is empty. * This is effectly a shortcut for {@code !hasLength(String)}. * <p>This method accepts any Object as an argument, comparing it to * {@code null} and the empty String. As a consequence, this method * will never return {@code true} for a non-null non-String object. * <p>The Object signature is useful for general attribute handling code * that commonly deals with Strings but generally has to iterate over * Objects since attributes may e.g. be primitive value objects as well. * <p><b>Note: If the object is typed to {@code String} upfront, prefer * {@link #hasLength(String)} or {@link #hasText(String)} instead.</b> * @param str the candidate object (possibly a {@code String}) * @since 3.2.1 * @see #hasLength(String) * @see #hasText(String) */ public static boolean isEmpty(@Nullable Object str) { return (str == null || "".equals(str)); } /** * Check that the given {@code CharSequence} is neither {@code null} nor * of length 0. * <p>Note: this method returns {@code true} for a {@code CharSequence} * that purely consists of whitespace. * <p><pre class="code"> * StringUtils.hasLength(null) = false * StringUtils.hasLength("") = false * StringUtils.hasLength(" ") = true * StringUtils.hasLength("Hello") = true * </pre> * @param str the {@code CharSequence} to check (may be {@code null}) * @return {@code true} if the {@code CharSequence} is not {@code null} and has length * @see #hasLength(String) * @see #hasText(CharSequence) */ public static boolean hasLength(@Nullable CharSequence str) { return (str != null && str.length() > 0); } /** * Check that the given {@code String} is neither {@code null} nor of length 0. * <p>Note: this method returns {@code true} for a {@code String} that * purely consists of whitespace. * @param str the {@code String} to check (may be {@code null}) * @return {@code true} if the {@code String} is not {@code null} and has length * @see #hasLength(CharSequence) * @see #hasText(String) */ public static boolean hasLength(@Nullable String str) { return (str != null && !str.isEmpty()); } /** * Check whether the given {@code CharSequence} contains actual <em>text</em>. * <p>More specifically, this method returns {@code true} if the * {@code CharSequence} is not {@code null}, its length is greater than * 0, and it contains at least one non-whitespace character. * <p><pre class="code"> * StringUtils.hasText(null) = false * StringUtils.hasText("") = false * StringUtils.hasText(" ") = false * StringUtils.hasText("12345") = true * StringUtils.hasText(" 12345 ") = true * </pre> * @param str the {@code CharSequence} to check (may be {@code null}) * @return {@code true} if the {@code CharSequence} is not {@code null}, * its length is greater than 0, and it does not contain whitespace only * @see #hasText(String) * @see #hasLength(CharSequence) * @see Character#isWhitespace */ public static boolean hasText(@Nullable CharSequence str) { return (str != null && str.length() > 0 && containsText(str)); } /** * Check whether the given {@code String} contains actual <em>text</em>. * <p>More specifically, this method returns {@code true} if the * {@code String} is not {@code null}, its length is greater than 0, * and it contains at least one non-whitespace character. * @param str the {@code String} to check (may be {@code null}) * @return {@code true} if the {@code String} is not {@code null}, its * length is greater than 0, and it does not contain whitespace only * @see #hasText(CharSequence) * @see #hasLength(String) * @see Character#isWhitespace */ public static boolean hasText(@Nullable String str) { return (str != null && !str.isEmpty() && containsText(str)); } private static boolean containsText(CharSequence str) { int strLen = str.length(); for (int i = 0; i < strLen; i++) { if (!Character.isWhitespace(str.charAt(i))) { return true; } } return false; } /** * Check whether the given {@code CharSequence} contains any whitespace characters. * @param str the {@code CharSequence} to check (may be {@code null}) * @return {@code true} if the {@code CharSequence} is not empty and * contains at least 1 whitespace character * @see Character#isWhitespace */ public static boolean containsWhitespace(@Nullable CharSequence str) { if (!hasLength(str)) { return false; } int strLen = str.length(); for (int i = 0; i < strLen; i++) { if (Character.isWhitespace(str.charAt(i))) { return true; } } return false; } /** * Check whether the given {@code String} contains any whitespace characters. * @param str the {@code String} to check (may be {@code null}) * @return {@code true} if the {@code String} is not empty and * contains at least 1 whitespace character * @see #containsWhitespace(CharSequence) */ public static boolean containsWhitespace(@Nullable String str) { return containsWhitespace((CharSequence) str); } /** * Trim leading and trailing whitespace from the given {@code String}. * @param str the {@code String} to check * @return the trimmed {@code String} * @see java.lang.Character#isWhitespace */ public static String trimWhitespace(String str) { if (!hasLength(str)) { return str; } int beginIndex = 0; int endIndex = str.length() - 1; while (beginIndex <= endIndex && Character.isWhitespace(str.charAt(beginIndex))) { beginIndex++; } while (endIndex > beginIndex && Character.isWhitespace(str.charAt(endIndex))) { endIndex--; } return str.substring(beginIndex, endIndex + 1); } /** * Trim <i>all</i> whitespace from the given {@code String}: * leading, trailing, and in between characters. * @param str the {@code String} to check * @return the trimmed {@code String} * @see java.lang.Character#isWhitespace */ public static String trimAllWhitespace(String str) { if (!hasLength(str)) { return str; } int len = str.length(); StringBuilder sb = new StringBuilder(str.length()); for (int i = 0; i < len; i++) { char c = str.charAt(i); if (!Character.isWhitespace(c)) { sb.append(c); } } return sb.toString(); } /** * Trim leading whitespace from the given {@code String}. * @param str the {@code String} to check * @return the trimmed {@code String} * @see java.lang.Character#isWhitespace */ public static String trimLeadingWhitespace(String str) { if (!hasLength(str)) { return str; } StringBuilder sb = new StringBuilder(str); while (sb.length() > 0 && Character.isWhitespace(sb.charAt(0))) { sb.deleteCharAt(0); } return sb.toString(); } /** * Trim trailing whitespace from the given {@code String}. * @param str the {@code String} to check * @return the trimmed {@code String} * @see java.lang.Character#isWhitespace */ public static String trimTrailingWhitespace(String str) { if (!hasLength(str)) { return str; } StringBuilder sb = new StringBuilder(str); while (sb.length() > 0 && Character.isWhitespace(sb.charAt(sb.length() - 1))) { sb.deleteCharAt(sb.length() - 1); } return sb.toString(); } /** * Trim all occurrences of the supplied leading character from the given {@code String}. * @param str the {@code String} to check * @param leadingCharacter the leading character to be trimmed * @return the trimmed {@code String} */ public static String trimLeadingCharacter(String str, char leadingCharacter) { if (!hasLength(str)) { return str; } StringBuilder sb = new StringBuilder(str); while (sb.length() > 0 && sb.charAt(0) == leadingCharacter) { sb.deleteCharAt(0); } return sb.toString(); } /** * Trim all occurrences of the supplied trailing character from the given {@code String}. * @param str the {@code String} to check * @param trailingCharacter the trailing character to be trimmed * @return the trimmed {@code String} */ public static String trimTrailingCharacter(String str, char trailingCharacter) { if (!hasLength(str)) { return str; } StringBuilder sb = new StringBuilder(str); while (sb.length() > 0 && sb.charAt(sb.length() - 1) == trailingCharacter) { sb.deleteCharAt(sb.length() - 1); } return sb.toString(); } /** * Test if the given {@code String} starts with the specified prefix, * ignoring upper/lower case. * @param str the {@code String} to check * @param prefix the prefix to look for * @see java.lang.String#startsWith */ public static boolean startsWithIgnoreCase(@Nullable String str, @Nullable String prefix) { return (str != null && prefix != null && str.length() >= prefix.length() && str.regionMatches(true, 0, prefix, 0, prefix.length())); } /** * Test if the given {@code String} ends with the specified suffix, * ignoring upper/lower case. * @param str the {@code String} to check * @param suffix the suffix to look for * @see java.lang.String#endsWith */ public static boolean endsWithIgnoreCase(@Nullable String str, @Nullable String suffix) { return (str != null && suffix != null && str.length() >= suffix.length() && str.regionMatches(true, str.length() - suffix.length(), suffix, 0, suffix.length())); } /** * Test whether the given string matches the given substring * at the given index. * @param str the original string (or StringBuilder) * @param index the index in the original string to start matching against * @param substring the substring to match at the given index */ public static boolean substringMatch(CharSequence str, int index, CharSequence substring) { if (index + substring.length() > str.length()) { return false; } for (int i = 0; i < substring.length(); i++) { if (str.charAt(index + i) != substring.charAt(i)) { return false; } } return true; } /** * Count the occurrences of the substring {@code sub} in string {@code str}. * @param str string to search in * @param sub string to search for */ public static int countOccurrencesOf(String str, String sub) { if (!hasLength(str) || !hasLength(sub)) { return 0; } int count = 0; int pos = 0; int idx; while ((idx = str.indexOf(sub, pos)) != -1) { ++count; pos = idx + sub.length(); } return count; } /** * Replace all occurrences of a substring within a string with another string. * @param inString {@code String} to examine * @param oldPattern {@code String} to replace * @param newPattern {@code String} to insert * @return a {@code String} with the replacements */ public static String replace(String inString, String oldPattern, @Nullable String newPattern) { if (!hasLength(inString) || !hasLength(oldPattern) || newPattern == null) { return inString; } int index = inString.indexOf(oldPattern); if (index == -1) { // no occurrence -> can return input as-is return inString; } int capacity = inString.length(); if (newPattern.length() > oldPattern.length()) { capacity += 16; } StringBuilder sb = new StringBuilder(capacity); int pos = 0; // our position in the old string int patLen = oldPattern.length(); while (index >= 0) { sb.append(inString.substring(pos, index)); sb.append(newPattern); pos = index + patLen; index = inString.indexOf(oldPattern, pos); } // append any characters to the right of a match sb.append(inString.substring(pos)); return sb.toString(); } /** * Delete all occurrences of the given substring. * @param inString the original {@code String} * @param pattern the pattern to delete all occurrences of * @return the resulting {@code String} */ public static String delete(String inString, String pattern) { return replace(inString, pattern, ""); } /** * Delete any character in a given {@code String}. * @param inString the original {@code String} * @param charsToDelete a set of characters to delete. * E.g. "az\n" will delete 'a's, 'z's and new lines. * @return the resulting {@code String} */ public static String deleteAny(String inString, @Nullable String charsToDelete) { if (!hasLength(inString) || !hasLength(charsToDelete)) { return inString; } StringBuilder sb = new StringBuilder(inString.length()); for (int i = 0; i < inString.length(); i++) { char c = inString.charAt(i); if (charsToDelete.indexOf(c) == -1) { sb.append(c); } } return sb.toString(); } //--------------------------------------------------------------------- // Convenience methods for working with formatted Strings //--------------------------------------------------------------------- /** * Quote the given {@code String} with single quotes. * @param str the input {@code String} (e.g. "myString") * @return the quoted {@code String} (e.g. "'myString'"), * or {@code null} if the input was {@code null} */ @Nullable public static String quote(@Nullable String str) { return (str != null ? "'" + str + "'" : null); } /** * Turn the given Object into a {@code String} with single quotes * if it is a {@code String}; keeping the Object as-is else. * @param obj the input Object (e.g. "myString") * @return the quoted {@code String} (e.g. "'myString'"), * or the input object as-is if not a {@code String} */ @Nullable public static Object quoteIfString(@Nullable Object obj) { return (obj instanceof String ? quote((String) obj) : obj); } /** * Unqualify a string qualified by a '.' dot character. For example, * "this.name.is.qualified", returns "qualified". * @param qualifiedName the qualified name */ public static String unqualify(String qualifiedName) { return unqualify(qualifiedName, '.'); } /** * Unqualify a string qualified by a separator character. For example, * "this:name:is:qualified" returns "qualified" if using a ':' separator. * @param qualifiedName the qualified name * @param separator the separator */ public static String unqualify(String qualifiedName, char separator) { return qualifiedName.substring(qualifiedName.lastIndexOf(separator) + 1); } /** * Capitalize a {@code String}, changing the first letter to * upper case as per {@link Character#toUpperCase(char)}. * No other letters are changed. * @param str the {@code String} to capitalize * @return the capitalized {@code String} */ public static String capitalize(String str) { return changeFirstCharacterCase(str, true); } /** * Uncapitalize a {@code String}, changing the first letter to * lower case as per {@link Character#toLowerCase(char)}. * No other letters are changed. * @param str the {@code String} to uncapitalize * @return the uncapitalized {@code String} */ public static String uncapitalize(String str) { return changeFirstCharacterCase(str, false); } private static String changeFirstCharacterCase(String str, boolean capitalize) { if (!hasLength(str)) { return str; } char baseChar = str.charAt(0); char updatedChar; if (capitalize) { updatedChar = Character.toUpperCase(baseChar); } else { updatedChar = Character.toLowerCase(baseChar); } if (baseChar == updatedChar) { return str; } char[] chars = str.toCharArray(); chars[0] = updatedChar; return new String(chars, 0, chars.length); } /** * Extract the filename from the given Java resource path, * e.g. {@code "mypath/myfile.txt" -> "myfile.txt"}. * @param path the file path (may be {@code null}) * @return the extracted filename, or {@code null} if none */ @Nullable public static String getFilename(@Nullable String path) { if (path == null) { return null; } int separatorIndex = path.lastIndexOf(FOLDER_SEPARATOR); return (separatorIndex != -1 ? path.substring(separatorIndex + 1) : path); } /** * Extract the filename extension from the given Java resource path, * e.g. "mypath/myfile.txt" -> "txt". * @param path the file path (may be {@code null}) * @return the extracted filename extension, or {@code null} if none */ @Nullable public static String getFilenameExtension(@Nullable String path) { if (path == null) { return null; } int extIndex = path.lastIndexOf(EXTENSION_SEPARATOR); if (extIndex == -1) { return null; } int folderIndex = path.lastIndexOf(FOLDER_SEPARATOR); if (folderIndex > extIndex) { return null; } return path.substring(extIndex + 1); } /** * Strip the filename extension from the given Java resource path, * e.g. "mypath/myfile.txt" -> "mypath/myfile". * @param path the file path * @return the path with stripped filename extension */ public static String stripFilenameExtension(String path) { int extIndex = path.lastIndexOf(EXTENSION_SEPARATOR); if (extIndex == -1) { return path; } int folderIndex = path.lastIndexOf(FOLDER_SEPARATOR); if (folderIndex > extIndex) { return path; } return path.substring(0, extIndex); } /** * Apply the given relative path to the given Java resource path, * assuming standard Java folder separation (i.e. "/" separators). * @param path the path to start from (usually a full file path) * @param relativePath the relative path to apply * (relative to the full file path above) * @return the full file path that results from applying the relative path */ public static String applyRelativePath(String path, String relativePath) { int separatorIndex = path.lastIndexOf(FOLDER_SEPARATOR); if (separatorIndex != -1) { String newPath = path.substring(0, separatorIndex); if (!relativePath.startsWith(FOLDER_SEPARATOR)) { newPath += FOLDER_SEPARATOR; } return newPath + relativePath; } else { return relativePath; } } /** * Normalize the path by suppressing sequences like "path/.." and * inner simple dots. * <p>The result is convenient for path comparison. For other uses, * notice that Windows separators ("\") are replaced by simple slashes. * @param path the original path * @return the normalized path */ public static String cleanPath(String path) { if (!hasLength(path)) { return path; } String pathToUse = replace(path, WINDOWS_FOLDER_SEPARATOR, FOLDER_SEPARATOR); // Shortcut if there is no work to do if (pathToUse.indexOf('.') == -1) { return pathToUse; } // Strip prefix from path to analyze, to not treat it as part of the // first path element. This is necessary to correctly parse paths like // "file:core/../core/io/Resource.class", where the ".." should just // strip the first "core" directory while keeping the "file:" prefix. int prefixIndex = pathToUse.indexOf(':'); String prefix = ""; if (prefixIndex != -1) { prefix = pathToUse.substring(0, prefixIndex + 1); if (prefix.contains(FOLDER_SEPARATOR)) { prefix = ""; } else { pathToUse = pathToUse.substring(prefixIndex + 1); } } if (pathToUse.startsWith(FOLDER_SEPARATOR)) { prefix = prefix + FOLDER_SEPARATOR; pathToUse = pathToUse.substring(1); } String[] pathArray = delimitedListToStringArray(pathToUse, FOLDER_SEPARATOR); LinkedList<String> pathElements = new LinkedList<>(); int tops = 0; for (int i = pathArray.length - 1; i >= 0; i--) { String element = pathArray[i]; if (CURRENT_PATH.equals(element)) { // Points to current directory - drop it. } else if (TOP_PATH.equals(element)) { // Registering top path found. tops++; } else { if (tops > 0) { // Merging path element with element corresponding to top path. tops--; } else { // Normal path element found. pathElements.add(0, element); } } } // Remaining top paths need to be retained. for (int i = 0; i < tops; i++) { pathElements.add(0, TOP_PATH); } // If nothing else left, at least explicitly point to current path. if (pathElements.size() == 1 && "".equals(pathElements.getLast()) && !prefix.endsWith(FOLDER_SEPARATOR)) { pathElements.add(0, CURRENT_PATH); } return prefix + collectionToDelimitedString(pathElements, FOLDER_SEPARATOR); } /** * Compare two paths after normalization of them. * @param path1 first path for comparison * @param path2 second path for comparison * @return whether the two paths are equivalent after normalization */ public static boolean pathEquals(String path1, String path2) { return cleanPath(path1).equals(cleanPath(path2)); } /** * Decode the given encoded URI component value. Based on the following rules: * <ul> * <li>Alphanumeric characters {@code "a"} through {@code "z"}, {@code "A"} through {@code "Z"}, * and {@code "0"} through {@code "9"} stay the same.</li> * <li>Special characters {@code "-"}, {@code "_"}, {@code "."}, and {@code "*"} stay the same.</li> * <li>A sequence "{@code %<i>xy</i>}" is interpreted as a hexadecimal representation of the character.</li> * </ul> * @param source the encoded String * @param charset the character set * @return the decoded value * @throws IllegalArgumentException when the given source contains invalid encoded sequences * @since 5.0 * @see java.net.URLDecoder#decode(String, String) */ public static String uriDecode(String source, Charset charset) { int length = source.length(); if (length == 0) { return source; } Assert.notNull(charset, "Charset must not be null"); ByteArrayOutputStream bos = new ByteArrayOutputStream(length); boolean changed = false; for (int i = 0; i < length; i++) { int ch = source.charAt(i); if (ch == '%') { if (i + 2 < length) { char hex1 = source.charAt(i + 1); char hex2 = source.charAt(i + 2); int u = Character.digit(hex1, 16); int l = Character.digit(hex2, 16); if (u == -1 || l == -1) { throw new IllegalArgumentException( "Invalid encoded sequence \"" + source.substring(i) + "\""); } bos.write((char) ((u << 4) + l)); i += 2; changed = true; } else { throw new IllegalArgumentException("Invalid encoded sequence \"" + source.substring(i) + "\""); } } else { bos.write(ch); } } return (changed ? new String(bos.toByteArray(), charset) : source); } /** * Parse the given {@code String} value into a {@link Locale}, accepting * the {@link Locale#toString} format as well as BCP 47 language tags. * @param localeValue the locale value: following either {@code Locale's} * {@code toString()} format ("en", "en_UK", etc), also accepting spaces as * separators (as an alternative to underscores), or BCP 47 (e.g. "en-UK") * as specified by {@link Locale#forLanguageTag} on Java 7+ * @return a corresponding {@code Locale} instance, or {@code null} if none * @throws IllegalArgumentException in case of an invalid locale specification * @since 5.0.4 * @see #parseLocaleString * @see Locale#forLanguageTag */ @Nullable public static Locale parseLocale(String localeValue) { String[] tokens = tokenizeLocaleSource(localeValue); if (tokens.length == 1) { validateLocalePart(localeValue); Locale resolved = Locale.forLanguageTag(localeValue); if (resolved.getLanguage().length() > 0) { return resolved; } } return parseLocaleTokens(localeValue, tokens); } /** * Parse the given {@code String} representation into a {@link Locale}. * <p>For many parsing scenarios, this is an inverse operation of * {@link Locale#toString Locale's toString}, in a lenient sense. * This method does not aim for strict {@code Locale} design compliance; * it is rather specifically tailored for typical Spring parsing needs. * <p><b>Note: This delegate does not accept the BCP 47 language tag format. * Please use {@link #parseLocale} for lenient parsing of both formats.</b> * @param localeString the locale {@code String}: following {@code Locale's} * {@code toString()} format ("en", "en_UK", etc), also accepting spaces as * separators (as an alternative to underscores) * @return a corresponding {@code Locale} instance, or {@code null} if none * @throws IllegalArgumentException in case of an invalid locale specification */ @Nullable public static Locale parseLocaleString(String localeString) { return parseLocaleTokens(localeString, tokenizeLocaleSource(localeString)); } private static String[] tokenizeLocaleSource(String localeSource) { return tokenizeToStringArray(localeSource, "_ ", false, false); } @Nullable private static Locale parseLocaleTokens(String localeString, String[] tokens) { String language = (tokens.length > 0 ? tokens[0] : ""); String country = (tokens.length > 1 ? tokens[1] : ""); validateLocalePart(language); validateLocalePart(country); String variant = ""; if (tokens.length > 2) { // There is definitely a variant, and it is everything after the country // code sans the separator between the country code and the variant. int endIndexOfCountryCode = localeString.indexOf(country, language.length()) + country.length(); // Strip off any leading '_' and whitespace, what's left is the variant. variant = trimLeadingWhitespace(localeString.substring(endIndexOfCountryCode)); if (variant.startsWith("_")) { variant = trimLeadingCharacter(variant, '_'); } } if (variant.isEmpty() && country.startsWith("#")) { variant = country; country = ""; } return (language.length() > 0 ? new Locale(language, country, variant) : null); } private static void validateLocalePart(String localePart) { for (int i = 0; i < localePart.length(); i++) { char ch = localePart.charAt(i); if (ch != ' ' && ch != '_' && ch != '-' && ch != '#' && !Character.isLetterOrDigit(ch)) { throw new IllegalArgumentException( "Locale part \"" + localePart + "\" contains invalid characters"); } } } /** * Determine the RFC 3066 compliant language tag, * as used for the HTTP "Accept-Language" header. * @param locale the Locale to transform to a language tag * @return the RFC 3066 compliant language tag as {@code String} * @deprecated as of 5.0.4, in favor of {@link Locale#toLanguageTag()} */ @Deprecated public static String toLanguageTag(Locale locale) { return locale.getLanguage() + (hasText(locale.getCountry()) ? "-" + locale.getCountry() : ""); } /** * Parse the given {@code timeZoneString} value into a {@link TimeZone}. * @param timeZoneString the time zone {@code String}, following {@link TimeZone#getTimeZone(String)} * but throwing {@link IllegalArgumentException} in case of an invalid time zone specification * @return a corresponding {@link TimeZone} instance * @throws IllegalArgumentException in case of an invalid time zone specification */ public static TimeZone parseTimeZoneString(String timeZoneString) { TimeZone timeZone = TimeZone.getTimeZone(timeZoneString); if ("GMT".equals(timeZone.getID()) && !timeZoneString.startsWith("GMT")) { // We don't want that GMT fallback... throw new IllegalArgumentException("Invalid time zone specification '" + timeZoneString + "'"); } return timeZone; } //--------------------------------------------------------------------- // Convenience methods for working with String arrays //--------------------------------------------------------------------- /** * Copy the given {@link Collection} into a {@code String} array. * <p>The {@code Collection} must contain {@code String} elements only. * @param collection the {@code Collection} to copy * (potentially {@code null} or empty) * @return the resulting {@code String} array */ public static String[] toStringArray(@Nullable Collection<String> collection) { return (!CollectionUtils.isEmpty(collection) ? collection.toArray(EMPTY_STRING_ARRAY) : EMPTY_STRING_ARRAY); } /** * Copy the given {@link Enumeration} into a {@code String} array. * <p>The {@code Enumeration} must contain {@code String} elements only. * @param enumeration the {@code Enumeration} to copy * (potentially {@code null} or empty) * @return the resulting {@code String} array */ public static String[] toStringArray(@Nullable Enumeration<String> enumeration) { return (enumeration != null ? toStringArray(Collections.list(enumeration)) : EMPTY_STRING_ARRAY); } /** * Append the given {@code String} to the given {@code String} array, * returning a new array consisting of the input array contents plus * the given {@code String}. * @param array the array to append to (can be {@code null}) * @param str the {@code String} to append * @return the new array (never {@code null}) */ public static String[] addStringToArray(@Nullable String[] array, String str) { if (ObjectUtils.isEmpty(array)) { return new String[] { str }; } String[] newArr = new String[array.length + 1]; System.arraycopy(array, 0, newArr, 0, array.length); newArr[array.length] = str; return newArr; } /** * Concatenate the given {@code String} arrays into one, * with overlapping array elements included twice. * <p>The order of elements in the original arrays is preserved. * @param array1 the first array (can be {@code null}) * @param array2 the second array (can be {@code null}) * @return the new array ({@code null} if both given arrays were {@code null}) */ @Nullable public static String[] concatenateStringArrays(@Nullable String[] array1, @Nullable String[] array2) { if (ObjectUtils.isEmpty(array1)) { return array2; } if (ObjectUtils.isEmpty(array2)) { return array1; } String[] newArr = new String[array1.length + array2.length]; System.arraycopy(array1, 0, newArr, 0, array1.length); System.arraycopy(array2, 0, newArr, array1.length, array2.length); return newArr; } /** * Merge the given {@code String} arrays into one, with overlapping * array elements only included once. * <p>The order of elements in the original arrays is preserved * (with the exception of overlapping elements, which are only * included on their first occurrence). * @param array1 the first array (can be {@code null}) * @param array2 the second array (can be {@code null}) * @return the new array ({@code null} if both given arrays were {@code null}) * @deprecated as of 4.3.15, in favor of manual merging via {@link LinkedHashSet} * (with every entry included at most once, even entries within the first array) */ @Deprecated @Nullable public static String[] mergeStringArrays(@Nullable String[] array1, @Nullable String[] array2) { if (ObjectUtils.isEmpty(array1)) { return array2; } if (ObjectUtils.isEmpty(array2)) { return array1; } List<String> result = new ArrayList<>(Arrays.asList(array1)); for (String str : array2) { if (!result.contains(str)) { result.add(str); } } return toStringArray(result); } /** * Sort the given {@code String} array if necessary. * @param array the original array (potentially empty) * @return the array in sorted form (never {@code null}) */ public static String[] sortStringArray(String[] array) { if (ObjectUtils.isEmpty(array)) { return array; } Arrays.sort(array); return array; } /** * Trim the elements of the given {@code String} array, * calling {@code String.trim()} on each of them. * @param array the original {@code String} array (potentially empty) * @return the resulting array (of the same size) with trimmed elements */ public static String[] trimArrayElements(String[] array) { if (ObjectUtils.isEmpty(array)) { return array; } String[] result = new String[array.length]; for (int i = 0; i < array.length; i++) { String element = array[i]; result[i] = (element != null ? element.trim() : null); } return result; } /** * Remove duplicate strings from the given array. * <p>As of 4.2, it preserves the original order, as it uses a {@link LinkedHashSet}. * @param array the {@code String} array (potentially empty) * @return an array without duplicates, in natural sort order */ public static String[] removeDuplicateStrings(String[] array) { if (ObjectUtils.isEmpty(array)) { return array; } Set<String> set = new LinkedHashSet<>(Arrays.asList(array)); return toStringArray(set); } /** * Split a {@code String} at the first occurrence of the delimiter. * Does not include the delimiter in the result. * @param toSplit the string to split (potentially {@code null} or empty) * @param delimiter to split the string up with (potentially {@code null} or empty) * @return a two element array with index 0 being before the delimiter, and * index 1 being after the delimiter (neither element includes the delimiter); * or {@code null} if the delimiter wasn't found in the given input {@code String} */ @Nullable public static String[] split(@Nullable String toSplit, @Nullable String delimiter) { if (!hasLength(toSplit) || !hasLength(delimiter)) { return null; } int offset = toSplit.indexOf(delimiter); if (offset < 0) { return null; } String beforeDelimiter = toSplit.substring(0, offset); String afterDelimiter = toSplit.substring(offset + delimiter.length()); return new String[] { beforeDelimiter, afterDelimiter }; } /** * Take an array of strings and split each element based on the given delimiter. * A {@code Properties} instance is then generated, with the left of the delimiter * providing the key, and the right of the delimiter providing the value. * <p>Will trim both the key and value before adding them to the {@code Properties}. * @param array the array to process * @param delimiter to split each element using (typically the equals symbol) * @return a {@code Properties} instance representing the array contents, * or {@code null} if the array to process was {@code null} or empty */ @Nullable public static Properties splitArrayElementsIntoProperties(String[] array, String delimiter) { return splitArrayElementsIntoProperties(array, delimiter, null); } /** * Take an array of strings and split each element based on the given delimiter. * A {@code Properties} instance is then generated, with the left of the * delimiter providing the key, and the right of the delimiter providing the value. * <p>Will trim both the key and value before adding them to the * {@code Properties} instance. * @param array the array to process * @param delimiter to split each element using (typically the equals symbol) * @param charsToDelete one or more characters to remove from each element * prior to attempting the split operation (typically the quotation mark * symbol), or {@code null} if no removal should occur * @return a {@code Properties} instance representing the array contents, * or {@code null} if the array to process was {@code null} or empty */ @Nullable public static Properties splitArrayElementsIntoProperties(String[] array, String delimiter, @Nullable String charsToDelete) { if (ObjectUtils.isEmpty(array)) { return null; } Properties result = new Properties(); for (String element : array) { if (charsToDelete != null) { element = deleteAny(element, charsToDelete); } String[] splittedElement = split(element, delimiter); if (splittedElement == null) { continue; } result.setProperty(splittedElement[0].trim(), splittedElement[1].trim()); } return result; } /** * Tokenize the given {@code String} into a {@code String} array via a * {@link StringTokenizer}. * <p>Trims tokens and omits empty tokens. * <p>The given {@code delimiters} string can consist of any number of * delimiter characters. Each of those characters can be used to separate * tokens. A delimiter is always a single character; for multi-character * delimiters, consider using {@link #delimitedListToStringArray}. * @param str the {@code String} to tokenize (potentially {@code null} or empty) * @param delimiters the delimiter characters, assembled as a {@code String} * (each of the characters is individually considered as a delimiter) * @return an array of the tokens * @see java.util.StringTokenizer * @see String#trim() * @see #delimitedListToStringArray */ public static String[] tokenizeToStringArray(@Nullable String str, String delimiters) { return tokenizeToStringArray(str, delimiters, true, true); } /** * Tokenize the given {@code String} into a {@code String} array via a * {@link StringTokenizer}. * <p>The given {@code delimiters} string can consist of any number of * delimiter characters. Each of those characters can be used to separate * tokens. A delimiter is always a single character; for multi-character * delimiters, consider using {@link #delimitedListToStringArray}. * @param str the {@code String} to tokenize (potentially {@code null} or empty) * @param delimiters the delimiter characters, assembled as a {@code String} * (each of the characters is individually considered as a delimiter) * @param trimTokens trim the tokens via {@link String#trim()} * @param ignoreEmptyTokens omit empty tokens from the result array * (only applies to tokens that are empty after trimming; StringTokenizer * will not consider subsequent delimiters as token in the first place). * @return an array of the tokens * @see java.util.StringTokenizer * @see String#trim() * @see #delimitedListToStringArray */ public static String[] tokenizeToStringArray(@Nullable String str, String delimiters, boolean trimTokens, boolean ignoreEmptyTokens) { if (str == null) { return EMPTY_STRING_ARRAY; } StringTokenizer st = new StringTokenizer(str, delimiters); List<String> tokens = new ArrayList<>(); while (st.hasMoreTokens()) { String token = st.nextToken(); if (trimTokens) { token = token.trim(); } if (!ignoreEmptyTokens || token.length() > 0) { tokens.add(token); } } return toStringArray(tokens); } /** * Take a {@code String} that is a delimited list and convert it into a * {@code String} array. * <p>A single {@code delimiter} may consist of more than one character, * but it will still be considered as a single delimiter string, rather * than as bunch of potential delimiter characters, in contrast to * {@link #tokenizeToStringArray}. * @param str the input {@code String} (potentially {@code null} or empty) * @param delimiter the delimiter between elements (this is a single delimiter, * rather than a bunch individual delimiter characters) * @return an array of the tokens in the list * @see #tokenizeToStringArray */ public static String[] delimitedListToStringArray(@Nullable String str, @Nullable String delimiter) { return delimitedListToStringArray(str, delimiter, null); } /** * Take a {@code String} that is a delimited list and convert it into * a {@code String} array. * <p>A single {@code delimiter} may consist of more than one character, * but it will still be considered as a single delimiter string, rather * than as bunch of potential delimiter characters, in contrast to * {@link #tokenizeToStringArray}. * @param str the input {@code String} (potentially {@code null} or empty) * @param delimiter the delimiter between elements (this is a single delimiter, * rather than a bunch individual delimiter characters) * @param charsToDelete a set of characters to delete; useful for deleting unwanted * line breaks: e.g. "\r\n\f" will delete all new lines and line feeds in a {@code String} * @return an array of the tokens in the list * @see #tokenizeToStringArray */ public static String[] delimitedListToStringArray(@Nullable String str, @Nullable String delimiter, @Nullable String charsToDelete) { if (str == null) { return EMPTY_STRING_ARRAY; } if (delimiter == null) { return new String[] { str }; } List<String> result = new ArrayList<>(); if (delimiter.isEmpty()) { for (int i = 0; i < str.length(); i++) { result.add(deleteAny(str.substring(i, i + 1), charsToDelete)); } } else { int pos = 0; int delPos; while ((delPos = str.indexOf(delimiter, pos)) != -1) { result.add(deleteAny(str.substring(pos, delPos), charsToDelete)); pos = delPos + delimiter.length(); } if (str.length() > 0 && pos <= str.length()) { // Add rest of String, but not in case of empty input. result.add(deleteAny(str.substring(pos), charsToDelete)); } } return toStringArray(result); } /** * Convert a comma delimited list (e.g., a row from a CSV file) into an * array of strings. * @param str the input {@code String} (potentially {@code null} or empty) * @return an array of strings, or the empty array in case of empty input */ public static String[] commaDelimitedListToStringArray(@Nullable String str) { return delimitedListToStringArray(str, ","); } /** * Convert a comma delimited list (e.g., a row from a CSV file) into a set. * <p>Note that this will suppress duplicates, and as of 4.2, the elements in * the returned set will preserve the original order in a {@link LinkedHashSet}. * @param str the input {@code String} (potentially {@code null} or empty) * @return a set of {@code String} entries in the list * @see #removeDuplicateStrings(String[]) */ public static Set<String> commaDelimitedListToSet(@Nullable String str) { String[] tokens = commaDelimitedListToStringArray(str); return new LinkedHashSet<>(Arrays.asList(tokens)); } /** * Convert a {@link Collection} to a delimited {@code String} (e.g. CSV). * <p>Useful for {@code toString()} implementations. * @param coll the {@code Collection} to convert (potentially {@code null} or empty) * @param delim the delimiter to use (typically a ",") * @param prefix the {@code String} to start each element with * @param suffix the {@code String} to end each element with * @return the delimited {@code String} */ public static String collectionToDelimitedString(@Nullable Collection<?> coll, String delim, String prefix, String suffix) { if (CollectionUtils.isEmpty(coll)) { return ""; } StringBuilder sb = new StringBuilder(); Iterator<?> it = coll.iterator(); while (it.hasNext()) { sb.append(prefix).append(it.next()).append(suffix); if (it.hasNext()) { sb.append(delim); } } return sb.toString(); } /** * Convert a {@code Collection} into a delimited {@code String} (e.g. CSV). * <p>Useful for {@code toString()} implementations. * @param coll the {@code Collection} to convert (potentially {@code null} or empty) * @param delim the delimiter to use (typically a ",") * @return the delimited {@code String} */ public static String collectionToDelimitedString(@Nullable Collection<?> coll, String delim) { return collectionToDelimitedString(coll, delim, "", ""); } /** * Convert a {@code Collection} into a delimited {@code String} (e.g., CSV). * <p>Useful for {@code toString()} implementations. * @param coll the {@code Collection} to convert (potentially {@code null} or empty) * @return the delimited {@code String} */ public static String collectionToCommaDelimitedString(@Nullable Collection<?> coll) { return collectionToDelimitedString(coll, ","); } /** * Convert a {@code String} array into a delimited {@code String} (e.g. CSV). * <p>Useful for {@code toString()} implementations. * @param arr the array to display (potentially {@code null} or empty) * @param delim the delimiter to use (typically a ",") * @return the delimited {@code String} */ public static String arrayToDelimitedString(@Nullable Object[] arr, String delim) { if (ObjectUtils.isEmpty(arr)) { return ""; } if (arr.length == 1) { return ObjectUtils.nullSafeToString(arr[0]); } StringJoiner sj = new StringJoiner(delim); for (Object o : arr) { sj.add(String.valueOf(o)); } return sj.toString(); } /** * Convert a {@code String} array into a comma delimited {@code String} * (i.e., CSV). * <p>Useful for {@code toString()} implementations. * @param arr the array to display (potentially {@code null} or empty) * @return the delimited {@code String} */ public static String arrayToCommaDelimitedString(@Nullable Object[] arr) { return arrayToDelimitedString(arr, ","); } }