Spring提供的工具類，主要用于框架內部使用，這個類提供了一些簡單的方法，并且提供了易于使用的方法在分割字符串，如CSV字符串，以及集合和數組。

StringUtils提供常用的方法如下：

判斷對象對象是否為null或者空字符串

public static boolean isEmpty(@Nullable Object str) {return (str == null || ''.equals(str));}

判斷給的序列是否為空或者length為0

public static boolean hasLength(@Nullable CharSequence str) {return (str != null && str.length() > 0);}public static boolean hasLength(@Nullable String str) {return (str != null && !str.isEmpty());}

判斷字符串是否以某個字符串開頭

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()));}

判斷字符串是否以某個字符串結尾

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()));}

用另一個字符串替換字符串中出現的所有子字符串

public static String replace(String inString, String oldPattern, @Nullable String newPattern) {if (!hasLength(inString) || !hasLength(oldPattern) || newPattern == null) {return inString;}//oldPattern字符串第一次出現的位置int index = inString.indexOf(oldPattern);if (index == -1) {// no occurrence -> can return input as-isreturn inString;}//字符串長度int capacity = inString.length();if (newPattern.length() > oldPattern.length()) {capacity += 16;}StringBuilder sb = new StringBuilder(capacity);int pos = 0; // our position in the old stringint patLen = oldPattern.length();while (index >= 0) {sb.append(inString, pos, index);sb.append(newPattern);pos = index + patLen;index = inString.indexOf(oldPattern, pos);}// append any characters to the right of a matchsb.append(inString, pos, inString.length());return sb.toString();}

根據給定的路徑規范化路徑

public static String cleanPath(String path) {if (!hasLength(path)) {return path;} //用新字符串替換舊字符串String pathToUse = replace(path, WINDOWS_FOLDER_SEPARATOR, FOLDER_SEPARATOR);// Shortcut if there is no work to doif (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);}

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