Spring强大的StringUtils工具类你会用吗
[ Spring学习 ] Spring 的 StringUtils 工具类这么强大 你会用那些方法 ?
:point_left: <stron> 🙏</stron>
💋如果对你有帮助，给博主一个免费的点赞💋 👋博客主页🎉 秋日的晚霞 ⭐️更多文章 请关注主页📝 👋一起走上java学习之路！ 🎄欢迎各位🔎点赞👍评论收藏⭐️🎄
[TOC]
🍃获取文件扩展名 getFilenameExtension
从给定的 Java 资源路径中提取文件扩展名，例如“mypathmyfile.txt”->“txt”。
//获取后缀文件名
String path = "D:\\API开发文档\\JAVA_API_1.8_CHS - 快捷方式";
String filenameExtension = StringUtils.getFilenameExtension(path);
System.out.println("filenameExtension = " + filenameExtension);
输出结果
filenameExtension = 8_CHS - 快捷方式
getFilenameExtension 的 源码
public static String getFilenameExtension(@Nullable String path) {
if (path == null) {
return null;
}
//EXTENSION_SEPARATOR = .
int extIndex = path.lastIndexOf(EXTENSION_SEPARATOR);
if (extIndex == -1) {
return null;
}
//FOLDER_SEPARATOR = /
int folderIndex = path.lastIndexOf(FOLDER_SEPARATOR);
if (folderIndex > extIndex) {
return null;
}
return path.substring(extIndex + 1);
}🍃获取文件扩展名 getFilenameExtension
从给定的 Java 资源路径中提取文件扩展名，例如“mypathmyfile.txt”->“txt”。
//获取后缀文件名
String path = "D:\\API开发文档\\JAVA_API_1.8_CHS - 快捷方式";
String filenameExtension = StringUtils.getFilenameExtension(path);
System.out.println("filenameExtension = " + filenameExtension);
输出结果
filenameExtension = 8_CHS - 快捷方式
getFilenameExtension 的 源码
public static String getFilenameExtension(@Nullable String path) {
if (path == null) {
return null;
}
//EXTENSION_SEPARATOR = .
int extIndex = path.lastIndexOf(EXTENSION_SEPARATOR);
if (extIndex == -1) {
return null;
}
//FOLDER_SEPARATOR = /
int folderIndex = path.lastIndexOf(FOLDER_SEPARATOR);
if (folderIndex > extIndex) {
return null;
}
return path.substring(extIndex + 1);
}🍃去除文件扩展名 stripFilenameExtension
public static void main(String[] args) {
String path = "D:\\API开发文档\\JAVA_API_1.8_CHS - 快捷方式";
String stripFilenameExtension = StringUtils.stripFilenameExtension(path);
System.out.println("stripFilenameExtension = " + stripFilenameExtension);
}
输出结果
filenameExtension = 8_CHS - 快捷方式
stripFilenameExtension 的 源码
public static String stripFilenameExtension(String path) {
int extIndex = path.lastIndexOf(EXTENSION_SEPARATOR);
if (extIndex == -1) {
return path;
}🍃替换所有的旧指定字符串 replace
用另一个字符串替换字符串中所有出现的子字符串
public static void main(String[] args) {
String str = "abcdefgabc";
String replace = StringUtils.replace(str,"abc","ABC");
System.out.println("replace = " + replace);
}
输出结果
replace = ABCdefgABC
replace 源码
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, 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, pos, inString.length());
return sb.toString();
}🍃删除所有的匹配字符串 delete
public static void main(String[] args) {
String str = "abcdefgabc";
String delete = StringUtils.delete(str,"abc");
System.out.println("delete = " + delete);
}
输出结果
delete = defg
delete 源码
public static String delete(String inString, String pattern) {
return replace(inString, pattern, "");
}
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, 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, pos, inString.length());
return sb.toString();
}
🍃判断对象是否为空 isEmpty
检查给定对象（可能是字符串）是否为空。这实际上是 !hasLength(String) 的快捷方式。
String s = "";
boolean flag = StringUtils.isEmpty(s );
System.out.println("flag = " + flag);
输出结果
flag = true
isEmpty源码
public static boolean isEmpty(@Nullable Object str) {
return (str == null || "".equals(str));
}🍃判断字符串是否有长度 hasLength
检查给定的 String 既不是 null 也不是长度为 0。 注意 hasLength 方法只能传入String类型的对象
String s = "";
boolean flag = StringUtils.hasLength(s);
System.out.println("flag = " + flag);输出结果
flag = false
hasLength源码
public static boolean hasLength(@Nullable String str) {
return (str != null && !str.isEmpty());
}🍃判断字符串是否有内容 hasText
检查给定的字符串是否包含实际文本。更具体地说，如果 String 不为 null，其长度大于 0，并且至少包含一个非空白字符，则此方法返回 true。
public static void main(String[] args) {
String s = "adsda qewq";
boolean flag = StringUtils.hasText(s);
System.out.println("flag = " + flag);
}输出结果
flag = true
hasText 源码
public static boolean hasText(@Nullable String str) {
return (str != null && !str.isEmpty() && containsText(str));
}🍃检查字符串是否有空白字符 containsWhitespace
检查给定的字符串是否包含任何空白字符。
public static void main(String[] args) {
String s = "adsda qewq";
boolean flag = StringUtils.containsWhitespace(s);
System.out.println("flag = " + flag);
}输出结果
flag = true
containsWhitespace 源码
public static boolean containsWhitespace(@Nullable String str) {
return containsWhitespace((CharSequence) str);
}
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;
}🍃去除字符串前后空白 trimWhitespace
*注意: 只会去除前后 不会去除中间空白 *
public static void main(String[] args) {
String s = " abcd efg ";
String trimWhitespace = StringUtils.trimWhitespace(s);
System.out.println("trimWhitespace = " + trimWhitespace);
}输出结果
trimWhitespace = abcd efg
trimWhitespace 源码
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);
}🍃去除字符串所有空白 trimAllWhitespace
修剪给定字符串中的所有空格：前导、尾随和字符之间。
public static void main(String[] args) {
String s = " abcd efg ";
String trimAllWhitespace = StringUtils.trimAllWhitespace(s);
System.out.println("trimAllWhitespace = " + trimAllWhitespace);
}
输出结果
trimAllWhitespace = abcdefg
trimAllWhitespace 源码
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();
}🍃去除字符串左边空格 trimLeadingWhitespace
从给定的字符串中修剪前导空格。
public static void main(String[] args) {
String s = " abcd efg ";
String trimLeadingWhitespace = StringUtils.trimLeadingWhitespace(s);
System.out.println("trimLeadingWhitespace = " + trimLeadingWhitespace);
}输出结果
trimLeadingWhitespace = abcd efg //注意空格到此
trimLeadingWhitespace 源码
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();
}🍃去除字符串右边空格 trimTrailingWhitespace
检查给定的字符串是否包含实际文本。更具体地说，如果 String 不为 null，其长度大于 0，并且至少包含一个非空白字符，则此方法返回 true。
public static void main(String[] args) {
String s = " abcd efg ";
String trimTrailingWhitespace = StringUtils.trimTrailingWhitespace(s);
System.out.println("trimTrailingWhitespace = " + trimTrailingWhitespace);
}输出结果
trimTrailingWhitespace = abcd efg
trimTrailingWhitespace 源码
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();
}
🍃删除字符串左边第一个给定字符 trimLeadingCharacter
public static void main(String[] args) {
String s = "abc abcd efg ";
String trimLeadingCharacter = StringUtils.trimLeadingCharacter(s,'a');
System.out.println("trimTrailingWhitespace = " + trimLeadingCharacter);
}输出结果
trimTrailingWhitespace = bc abcd efg
trimLeadingCharacter 源码
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();
}🍃删除字符串右边第一个给定字符 trimTrailingCharacter
检查给定的字符串是否包含实际文本。更具体地说，如果 String 不为 null，其长度大于 0，并且至少包含一个非空白字符，则此方法返回 true。
public static void main(String[] args) {
String s = "abc abcd efg a";
String trimTrailingCharacter = StringUtils.trimTrailingCharacter(s,'a');
System.out.println("trimTrailingWhitespace = " + trimTrailingCharacter);
}输出结果
trimTrailingWhitespace = abc abcd efg //空格到此
trimTrailingCharacter 源码
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();
}🍃判断字符串是否以给定字符串开头(忽略大小写) startsWithIgnoreCase
public static void main(String[] args) {
String s = "Abc abcd efg aBC";
boolean startsWithIgnoreCase = StringUtils.startsWithIgnoreCase(s, "abc");
System.out.println("startsWithIgnoreCase = " + startsWithIgnoreCase);
}输出结果
startsWithIgnoreCase = true
startsWithIgnoreCase 源码
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()));
}🍃判断字符串是否以给定字符串结尾 (忽略大小写) endsWithIgnoreCase
public static void main(String[] args) {
String s = "Abc abcd efg aBC";
boolean endsWithIgnoreCase = StringUtils.endsWithIgnoreCase(s, "abc");
System.out.println("startsWithIgnoreCase = " + endsWithIgnoreCase);
}输出结果
startsWithIgnoreCase = true
startsWithIgnoreCase 源码
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()));
}#Java求职##Spring##学习路径#
查看11道真题和解析
