辅助字符串处理类：org.apache.commons.lang3.StringUtils
api 地址：http://commons.apache.org/proper/commons-lang/apidocs/index.html?index-all.html
StringUtils 常用方法：
| 方法 | 作用 |
|---|---|
| isBlank | 判断某字符串是否为空、长度为0、由空白符(whitespace) 构成。isBlank(" ")为true。多数情况用 isBlank |
| isEmpty | 判断某字符串是否为空，为空的标准是 strnull 或 str.length()0。isEmpty(" ")为false |
| trim | 去掉字符串两端的控制符(control characters, char <= 32)。如果为null或""，则返回null |
| strip | 去掉字符串两端的空白符(whitespace)。如果输入为null则返回null |
- StringUtils 说明：
Operations on String that are null safe.
IsEmpty/IsBlank - checks if a String contains text
Trim/Strip - removes leading and trailing whitespace
Equals/Compare - compares two strings null-safe
startsWith - check if a String starts with a prefix null-safe
endsWith - check if a String ends with a suffix null-safe
IndexOf/LastIndexOf/Contains - null-safe index-of checks
IndexOfAny/LastIndexOfAny/IndexOfAnyBut/LastIndexOfAnyBut - index-of any of a set of Strings
ContainsOnly/ContainsNone/ContainsAny - does String contains only/none/any of these characters
Substring/Left/Right/Mid - null-safe substring extractions
SubstringBefore/SubstringAfter/SubstringBetween - substring extraction relative to other strings
Split/Join - splits a String into an array of substrings and vice versa
Remove/Delete - removes part of a String
Replace/Overlay - Searches a String and replaces one String with another
Chomp/Chop - removes the last part of a String
AppendIfMissing - appends a suffix to the end of the String if not present
PrependIfMissing - prepends a prefix to the start of the String if not present
LeftPad/RightPad/Center/Repeat - pads a String
UpperCase/LowerCase/SwapCase/Capitalize/Uncapitalize - changes the case of a String
CountMatches - counts the number of occurrences of one String in another
IsAlpha/IsNumeric/IsWhitespace/IsAsciiPrintable - checks the characters in a String
DefaultString - protects against a null input String
Rotate - rotate (circular shift) a String
Reverse/ReverseDelimited - reverses a String
Abbreviate - abbreviates a string using ellipsis or another given String
Difference - compares Strings and reports on their differences
LevenshteinDistance - the number of changes needed to change one String into another
The StringUtils class defines certain words related to String handling.
null - null
empty - a zero-length string ("")
space - the space character (' ', char 32)
whitespace - the characters defined by Character.isWhitespace(char)
trim - the characters <= 32 as in String.trim()
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