isEmpty 和 isBlank 的用法区别,至少一半的人答不上来...
二哥编程知识星球 (戳链接加入)正式上线了,来和 370 多名 小伙伴一起打怪升级吧!这是一个 Java 学习指南 + 编程实战的私密圈子,你可以向二哥提问、帮你制定学习计划、跟着二哥一起做实战项目,冲冲冲。
Java程序员进阶之路网址:https://tobebetterjavaer.com
大家好,我是二哥,开发中经常有些小细节容易忽略,这些小细节往往容易导致代码缺陷,今天分享一波工具类的小细节
也许你两个都不知道,也许你除了isEmpty
/isNotEmpty
/isNotBlank
/isBlank
外,并不知道还有isAnyEmpty
/isNoneEmpty
/isAnyBlank
/isNoneBlank
的存在, come on ,让我们一起来探索org.apache.commons.lang3.StringUtils;
这个工具类。
isEmpty 系列
StringUtils.isEmpty()
是否为空. 可以看到 " " 空格是会绕过这种空判断,因为是一个空格,并不是严格的空值,会导致 isEmpty(" ")=false
StringUtils.isEmpty(null) = true
StringUtils.isEmpty("") = true
StringUtils.isEmpty(" ") = false
StringUtils.isEmpty("bob") = false
StringUtils.isEmpty(" bob ") = false
/**
*
* <p>NOTE: This method changed in Lang version 2.0.
* It no longer trims the CharSequence.
* That functionality is available in isBlank().</p>
*
* @param cs the CharSequence to check, may be null
* @return {@code true} if the CharSequence is empty or null
* @since 3.0 Changed signature from isEmpty(String) to isEmpty(CharSequence)
*/
public static boolean isEmpty(final CharSequence cs) {
return cs == null || cs.length() == 0;
}
StringUtils.isNotEmpty()
相当于不为空 , = !isEmpty()
。
public static boolean isNotEmpty(final CharSequence cs) {
return !isEmpty(cs);
}
StringUtils.isAnyEmpty()
是否有一个为空,只有一个为空,就为 true。
StringUtils.isAnyEmpty(null) = true
StringUtils.isAnyEmpty(null, "foo") = true
StringUtils.isAnyEmpty("", "bar") = true
StringUtils.isAnyEmpty("bob", "") = true
StringUtils.isAnyEmpty(" bob ", null) = true
StringUtils.isAnyEmpty(" ", "bar") = false
StringUtils.isAnyEmpty("foo", "bar") = false
/**
* @param css the CharSequences to check, may be null or empty
* @return {@code true} if any of the CharSequences are empty or null
* @since 3.2
*/
public static boolean isAnyEmpty(final CharSequence... css) {
if (ArrayUtils.isEmpty(css)) {
return true;
}
for (final CharSequence cs : css){
if (isEmpty(cs)) {
return true;
}
}
return false;
}
StringUtils.isNoneEmpty()
相当于!isAnyEmpty(css)
, 必须所有的值都不为空才返回 true
/**
* <p>Checks if none of the CharSequences are empty ("") or null.</p>
*
* <pre>
* StringUtils.isNoneEmpty(null) = false
* StringUtils.isNoneEmpty(null, "foo") = false
* StringUtils.isNoneEmpty("", "bar") = false
* StringUtils.isNoneEmpty("bob", "") = false
* StringUtils.isNoneEmpty(" bob ", null) = false
* StringUtils.isNoneEmpty(" ", "bar") = true
* StringUtils.isNoneEmpty("foo", "bar") = true
* </pre>
*
* @param css the CharSequences to check, may be null or empty
* @return {@code true} if none of the CharSequences are empty or null
* @since 3.2
*/
public static boolean isNoneEmpty(final CharSequence... css) {
isBank 系列
StringUtils.isBlank()
是否为真空值(空格或者空值)
StringUtils.isBlank(null) = true
StringUtils.isBlank("") = true
StringUtils.isBlank(" ") = true
StringUtils.isBlank("bob") = false
StringUtils.isBlank(" bob ") = false
/**
* <p>Checks if a CharSequence is whitespace, empty ("") or null.</p>
* @param cs the CharSequence to check, may be null
* @return {@code true} if the CharSequence is null, empty or whitespace
* @since 2.0
* @since 3.0 Changed signature from isBlank(String) to isBlank(CharSequence)
*/
public static boolean isBlank(final CharSequence cs) {
int strLen;
if (cs == null || (strLen = cs.length()) == 0) {
return true;
}
for (int i = 0; i < strLen; i++) {
if (Character.isWhitespace(cs.charAt(i)) == false) {
return false;
}
}
return true;
}
StringUtils.isNotBlank()
是否真的不为空,不是空格或者空值 ,相当于!isBlank();
public static boolean isNotBlank(final CharSequence cs) {
return !isBlank(cs);
}
StringUtils.isAnyBlank()
是否包含任何真空值(包含空格或空值)
StringUtils.isAnyBlank(null) = true
StringUtils.isAnyBlank(null, "foo") = true
StringUtils.isAnyBlank(null, null) = true
StringUtils.isAnyBlank("", "bar") = true
StringUtils.isAnyBlank("bob", "") = true
StringUtils.isAnyBlank(" bob ", null) = true
StringUtils.isAnyBlank(" ", "bar") = true
StringUtils.isAnyBlank("foo", "bar") = false
/**
* <p>Checks if any one of the CharSequences are blank ("") or null and not whitespace only..</p>
* @param css the CharSequences to check, may be null or empty
* @return {@code true} if any of the CharSequences are blank or null or whitespace only
* @since 3.2
*/
public static boolean isAnyBlank(final CharSequence... css) {
if (ArrayUtils.isEmpty(css)) {
return true;
}
for (final CharSequence cs : css){
if (isBlank(cs)) {
return true;
}
}
return false;
}
StringUtils.isNoneBlank()
是否全部都不包含空值或空格
StringUtils.isNoneBlank(null) = false
StringUtils.isNoneBlank(null, "foo") = false
StringUtils.isNoneBlank(null, null) = false
StringUtils.isNoneBlank("", "bar") = false
StringUtils.isNoneBlank("bob", "") = false
StringUtils.isNoneBlank(" bob ", null) = false
StringUtils.isNoneBlank(" ", "bar") = false
StringUtils.isNoneBlank("foo", "bar") = true
/**
* <p>Checks if none of the CharSequences are blank ("") or null and whitespace only..</p>
* @param css the CharSequences to check, may be null or empty
* @return {@code true} if none of the CharSequences are blank or null or whitespace only
* @since 3.2
*/
public static boolean isNoneBlank(final CharSequence... css) {
return !isAnyBlank(css);
}
StringUtils 的其他方法
可以参考官方的文档,里面有详细的描述,有些方法还是很好用的。
https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/StringUtils.html
方法名 | 英文解释 | 中文解释 |
---|---|---|
IsEmpty/IsBlank | checks if a String contains text | 检查字符串是否包含文本 |
Trim/Strip | removes leading and trailing whitespace | 删除前导和尾随空格 |
Equals/Compare | compares two strings null-safe | 比较两个字符串是否为 null 安全的 |
startsWith | check if a String starts with a prefix null-safe | 检查字符串是否以前缀 null 安全开头 |
endsWith | check if a String ends with a suffix null-safe | 检查字符串是否以后缀 null 安全结尾 |
IndexOf/LastIndexOf/Contains | null-safe index-of checks | 包含空安全索引检查 |
IndexOfAny/LastIndexOfAny/IndexOfAnyBut/LastIndexOfAnyBut | index-of any of a set of Strings | 任意一组字符串的索引 |
ContainsOnly/ContainsNone/ContainsAny | does String contains only/none/any of these characters | 字符串是否仅包含/无/这些字符中的任何一个 |
Substring/Left/Right/Mid | null-safe substring extractions | 字符串安全提取 |
SubstringBefore/SubstringAfter/SubstringBetween | substring extraction relative to other strings -相对其他字符串的字符串提取 | |
Split/Join | splits a String into an array of substrings and vice versa | 将字符串拆分为子字符串数组,反之亦然 |
Remove/Delete | removes part of a String -删除字符串的一部分 | |
Replace/Overlay | Searches a String and replaces one String with another | 搜索字符串,然后用另一个字符串替换 |
Chomp/Chop | removes the last part of a String | 删除字符串的最后一部分 |
AppendIfMissing | appends a suffix to the end of the String if not present | 如果不存在后缀,则在字符串的末尾附加一个后缀 |
PrependIfMissing | prepends a prefix to the start of the String if not present | 如果不存在前缀,则在字符串的开头添加前缀 |
LeftPad/RightPad/Center/Repeat | pads a String | 填充字符串 |
UpperCase/LowerCase/SwapCase/Capitalize/Uncapitalize | changes the case of a String | 更改字符串的大小写 |
CountMatches | counts the number of occurrences of one String in another | 计算一个字符串在另一个字符串中出现的次数 |
IsAlpha/IsNumeric/IsWhitespace/IsAsciiPrintable | checks the characters in a String | 检查字符串中的字符 |
DefaultString | protects against a null input String | 防止输入字符串为空 |
Rotate | rotate (circular shift) a String | 旋转(循环移位)字符串 |
Reverse/ReverseDelimited | reverses a String -反转字符串 | |
Abbreviate | abbreviates a string using ellipsis or another given String | 使用省略号或另一个给定的 String 缩写一个字符串 |
Difference | compares Strings and reports on their differences | 比较字符串并报告其差异 |
LevenshteinDistance | the number of changes needed to change one String into another | 将一个 String 转换为另一个 String 所需的更改次数 |
程序汪资料链接
转载链接:https://mp.weixin.qq.com/s?__biz=MzA4NzQ0Njc4Ng==&mid=2247504624&idx=1&sn=c47e5413aa4914c7301970e0d217bc88&chksm=903bd69da74c5f8b4d4dc6683b4e34b2750278df3dcb9d13b129e80bad9a435b3d98e4ad3fe6#rd,出处:我是程序汪,整理:沉默王二