開發中經常有些小細節容易忽略，這些小細節往往容易導致代碼缺陷，今天分享一波工具類的小細節

也許你兩個都不知道,也許你除了isEmpty/isNotEmpty/isNotBlank/isBlank外,并不知道還有isAnyEmpty/isNoneEmpty/isAnyBlank/isNoneBlank的存在, come on ,讓我們一起來探索org.apache.commons.lang3.StringUtils;這個工具類。

isEmpty系列

StringUtils.isEmpty()

是否為空. 可以看到 " " 空格是會繞過這種空判斷,因為是一個空格,并不是嚴格的空值,會導致isEmpty(" ")=false

StringUtils.isEmpty(null)=true
StringUtils.isEmpty("")=true
StringUtils.isEmpty("")=false
StringUtils.isEmpty("bob")=false
StringUtils.isEmpty("bob")=false
/**
*
*
NOTE:ThismethodchangedinLangversion2.0.
*ItnolongertrimstheCharSequence.
*ThatfunctionalityisavailableinisBlank().
*
*@paramcstheCharSequencetocheck,maybenull
*@return{@codetrue}iftheCharSequenceisemptyornull
*@since3.0ChangedsignaturefromisEmpty(String)toisEmpty(CharSequence)
*/
publicstaticbooleanisEmpty(finalCharSequencecs){
returncs==null||cs.length()==0;
}

StringUtils.isNotEmpty()

相當于不為空 ,= !isEmpty()。

publicstaticbooleanisNotEmpty(finalCharSequencecs){
return!isEmpty(cs);
}

StringUtils.isAnyEmpty()

是否有一個為空,只有一個為空,就為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
/**
*@paramcsstheCharSequencestocheck,maybenullorempty
*@return{@codetrue}ifanyoftheCharSequencesareemptyornull
*@since3.2
*/
publicstaticbooleanisAnyEmpty(finalCharSequence...css){
if(ArrayUtils.isEmpty(css)){
returntrue;
}
for(finalCharSequencecs:css){
if(isEmpty(cs)){
returntrue;
}
}
returnfalse;
}

StringUtils.isNoneEmpty()

相當于!isAnyEmpty(css), 必須所有的值都不為空才返回true

/**
*
ChecksifnoneoftheCharSequencesareempty("")ornull.
*
*
*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
*
*
*@paramcsstheCharSequencestocheck,maybenullorempty
*@return{@codetrue}ifnoneoftheCharSequencesareemptyornull
*@since3.2
*/
publicstaticbooleanisNoneEmpty(finalCharSequence...css){

isBank系列

StringUtils.isBlank()

是否為真空值(空格或者空值)

StringUtils.isBlank(null)=true
StringUtils.isBlank("")=true
StringUtils.isBlank("")=true
StringUtils.isBlank("bob")=false
StringUtils.isBlank("bob")=false
/**
*
ChecksifaCharSequenceiswhitespace,empty("")ornull.
*@paramcstheCharSequencetocheck,maybenull
*@return{@codetrue}iftheCharSequenceisnull,emptyorwhitespace
*@since2.0
*@since3.0ChangedsignaturefromisBlank(String)toisBlank(CharSequence)
*/
publicstaticbooleanisBlank(finalCharSequencecs){
intstrLen;
if(cs==null||(strLen=cs.length())==0){
returntrue;
}
for(inti=0;iif(Character.isWhitespace(cs.charAt(i))==false){
returnfalse;
}
}
returntrue;
}

StringUtils.isNotBlank()

是否真的不為空,不是空格或者空值 ,相當于!isBlank();

publicstaticbooleanisNotBlank(finalCharSequencecs){
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
/**
*
ChecksifanyoneoftheCharSequencesareblank("")ornullandnotwhitespaceonly..
*@paramcsstheCharSequencestocheck,maybenullorempty
*@return{@codetrue}ifanyoftheCharSequencesareblankornullorwhitespaceonly
*@since3.2
*/
publicstaticbooleanisAnyBlank(finalCharSequence...css){
if(ArrayUtils.isEmpty(css)){
returntrue;
}
for(finalCharSequencecs:css){
if(isBlank(cs)){
returntrue;
}
}
returnfalse;
}

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
/**
*
ChecksifnoneoftheCharSequencesareblank("")ornullandwhitespaceonly..
*@paramcsstheCharSequencestocheck,maybenullorempty
*@return{@codetrue}ifnoneoftheCharSequencesareblankornullorwhitespaceonly
*@since3.2
*/
publicstaticbooleanisNoneBlank(finalCharSequence...css){
return!isAnyBlank(css);
}

StringUtils的其他方法

可以參考官方的文檔,里面有詳細的描述,有些方法還是很好用的。

https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/StringUtils.html

方法名	英文解釋	中文解釋
IsEmpty/IsBlank	checks if a String contains text	檢查字符串是否包含文本
Trim/Strip	removes leading and trailing whitespace	刪除前導和尾隨空格
Equals/Compare	compares two strings null-safe	比較兩個字符串是否為null安全的
startsWith	check if a String starts with a prefix null-safe	檢查字符串是否以前綴null安全開頭
endsWith	check if a String ends with a suffix null-safe	檢查字符串是否以后綴null安全結尾
IndexOf/LastIndexOf/Contains	null-safe index-of checks	包含空安全索引檢查
IndexOfAny/LastIndexOfAny/IndexOfAnyBut/LastIndexOfAnyBut	index-of any of a set of Strings	任意一組字符串的索引
ContainsOnly/ContainsNone/ContainsAny	does String contains only/none/any of these characters	字符串是否僅包含/無/這些字符中的任何一個
Substring/Left/Right/Mid	null-safe substring extractions	字符串安全提取
SubstringBefore/SubstringAfter/SubstringBetween	substring extraction relative to other strings -相對其他字符串的字符串提取
Split/Join	splits a String into an array of substrings and vice versa	將字符串拆分為子字符串數組，反之亦然
Remove/Delete	removes part of a String -刪除字符串的一部分
Replace/Overlay	Searches a String and replaces one String with another	搜索字符串，然后用另一個字符串替換
Chomp/Chop	removes the last part of a String	刪除字符串的最后一部分
AppendIfMissing	appends a suffix to the end of the String if not present	如果不存在后綴，則在字符串的末尾附加一個后綴
PrependIfMissing	prepends a prefix to the start of the String if not present	如果不存在前綴，則在字符串的開頭添加前綴
LeftPad/RightPad/Center/Repeat	pads a String	填充字符串
UpperCase/LowerCase/SwapCase/Capitalize/Uncapitalize	changes the case of a String	更改字符串的大小寫
CountMatches	counts the number of occurrences of one String in another	計算一個字符串在另一個字符串中出現的次數
IsAlpha/IsNumeric/IsWhitespace/IsAsciiPrintable	checks the characters in a String	檢查字符串中的字符
DefaultString	protects against a null input String	防止輸入字符串為空
Rotate	rotate (circular shift) a String	旋轉（循環移位）字符串
Reverse/ReverseDelimited	reverses a String -反轉字符串
Abbreviate	abbreviates a string using ellipsis or another given String	使用省略號或另一個給定的String縮寫一個字符串
Difference	compares Strings and reports on their differences	比較字符串并報告其差異
LevenshteinDistance	the number of changes needed to change one String into another	將一個String轉換為另一個String所需的更改次數

審核編輯：湯梓紅