StringUtils (com.xingyuv:captcha-plus 1.0.2 API)

java.lang.Object
- com.xingyuv.captcha.util.StringUtils

```
public class StringUtils
extends Object
```

字段概要

字段
限定符和类型	字段和说明
`static String`	`EMPTY` The empty String `""`.
`static int`	`INDEX_NOT_FOUND` Represents a failed index search.
`private static int`	`PAD_LIMIT` The maximum size to which the padding constant(s) can expand.

构造器概要

构造器
构造器和说明

StringUtils()
StringUtils instances should NOT be constructed in standard programming.

构造器
构造器和说明
`StringUtils()` `StringUtils` instances should NOT be constructed in standard programming.

方法概要

所有方法静态方法具体方法已过时的方法
限定符和类型	方法和说明
`static String`	`clean(String str)` 已过时。 Use the clearer named `trimToEmpty(String)`. Method will be removed in Commons Lang 3.0.
`static boolean`	`contains(String str, char searchChar)` Checks if String contains a search character, handling `null`.
`static boolean`	`contains(String str, String searchStr)` Checks if String contains a search String, handling `null`.
`static boolean`	`containsIgnoreCase(String str, String searchStr)` Checks if String contains a search String irrespective of case, handling `null`.
`static boolean`	`equals(String str1, String str2)` Compares two Strings, returning `true` if they are equal.
`static boolean`	`equalsIgnoreCase(String str1, String str2)` Compares two Strings, returning `true` if they are equal ignoring the case.
`static int`	`indexOf(String str, char searchChar)` Finds the first index within a String, handling `null`.
`static int`	`indexOf(String str, char searchChar, int startPos)` Finds the first index within a String from a start position, handling `null`.
`static int`	`indexOf(String str, String searchStr)` Finds the first index within a String, handling `null`.
`static int`	`indexOf(String str, String searchStr, int startPos)` Finds the first index within a String, handling `null`.
`static int`	`indexOfAny(String str, String[] searchStrs)` Find the first index of any of a set of potential substrings.
`static int`	`indexOfIgnoreCase(String str, String searchStr)` Case in-sensitive find of the first index within a String.
`static int`	`indexOfIgnoreCase(String str, String searchStr, int startPos)` Case in-sensitive find of the first index within a String from the specified position.
`static boolean`	`isBlank(String str)` Checks if a String is whitespace, empty ("") or null.
`static boolean`	`isEmpty(String str)` Checks if a String is empty ("") or null.
`static boolean`	`isNotBlank(String str)` Checks if a String is not empty (""), not null and not whitespace only.
`static boolean`	`isNotEmpty(String str)` Checks if a String is not empty ("") and not null.
`static int`	`lastIndexOf(String str, char searchChar)` Finds the last index within a String, handling `null`.
`static int`	`lastIndexOf(String str, char searchChar, int startPos)` Finds the last index within a String from a start position, handling `null`.
`static int`	`lastIndexOf(String str, String searchStr)` Finds the last index within a String, handling `null`.
`static int`	`lastIndexOf(String str, String searchStr, int startPos)` Finds the first index within a String, handling `null`.
`static int`	`lastIndexOfAny(String str, String[] searchStrs)` Find the latest index of any of a set of potential substrings.
`static int`	`lastIndexOfIgnoreCase(String str, String searchStr)` Case in-sensitive find of the last index within a String.
`static int`	`lastIndexOfIgnoreCase(String str, String searchStr, int startPos)` Case in-sensitive find of the last index within a String from the specified position.
`static int`	`lastOrdinalIndexOf(String str, String searchStr, int ordinal)` Finds the n-th last index within a String, handling `null`.
`static String`	`left(String str, int len)` Gets the leftmost `len` characters of a String.
`static String`	`mid(String str, int pos, int len)` Gets `len` characters from the middle of a String.
`static int`	`ordinalIndexOf(String str, String searchStr, int ordinal)` Finds the n-th index within a String, handling `null`.
`private static int`	`ordinalIndexOf(String str, String searchStr, int ordinal, boolean lastIndex)` Finds the n-th index within a String, handling `null`.
`static String`	`right(String str, int len)` Gets the rightmost `len` characters of a String.
`static String`	`strip(String str)` Strips whitespace from the start and end of a String.
`static String`	`strip(String str, String stripChars)` Strips any of a set of characters from the start and end of a String.
`static String[]`	`stripAll(String[] strs)` Strips whitespace from the start and end of every String in an array.
`static String[]`	`stripAll(String[] strs, String stripChars)` Strips any of a set of characters from the start and end of every String in an array.
`static String`	`stripEnd(String str, String stripChars)` Strips any of a set of characters from the end of a String.
`static String`	`stripStart(String str, String stripChars)` Strips any of a set of characters from the start of a String.
`static String`	`stripToEmpty(String str)` Strips whitespace from the start and end of a String returning an empty String if `null` input.
`static String`	`stripToNull(String str)` Strips whitespace from the start and end of a String returning `null` if the String is empty ("") after the strip.
`static String`	`substring(String str, int start)` Gets a substring from the specified String avoiding exceptions.
`static String`	`substring(String str, int start, int end)` Gets a substring from the specified String avoiding exceptions.
`static String`	`substringAfter(String str, String separator)` Gets the substring after the first occurrence of a separator.
`static String`	`substringAfterLast(String str, String separator)` Gets the substring after the last occurrence of a separator.
`static String`	`substringBefore(String str, String separator)` Gets the substring before the first occurrence of a separator.
`static String`	`substringBeforeLast(String str, String separator)` Gets the substring before the last occurrence of a separator.
`static String`	`substringBetween(String str, String tag)` Gets the String that is nested in between two instances of the same String.
`static String`	`substringBetween(String str, String open, String close)` Gets the String that is nested in between two Strings.
`static String`	`trim(String str)` Removes control characters (char <= 32) from both ends of this String, handling `null` by returning `null`.
`static String`	`trimToEmpty(String str)` Removes control characters (char <= 32) from both ends of this String returning an empty String ("") if the String is empty ("") after the trim or if it is `null`.
`static String`	`trimToNull(String str)` Removes control characters (char <= 32) from both ends of this String returning `null` if the String is empty ("") after the trim or if it is `null`.

从类继承的方法 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

字段详细资料
- EMPTY
```
public static final String EMPTY
```
  The empty String "".
  
  从以下版本开始:
  
  2.0
  
  另请参阅:
  
  常量字段值
- INDEX_NOT_FOUND
```
public static final int INDEX_NOT_FOUND
```
  Represents a failed index search.
  
  从以下版本开始:
  
  2.1
  
  另请参阅:
  
  常量字段值
- PAD_LIMIT
```
private static final int PAD_LIMIT
```
  The maximum size to which the padding constant(s) can expand.
  
  另请参阅:
  
  常量字段值

构造器详细资料
- StringUtils
```
public StringUtils()
```
  StringUtils instances should NOT be constructed in standard programming. Instead, the class should be used as StringUtils.trim(" foo ");.
  
  This constructor is public to permit tools that require a JavaBean instance to operate.

方法详细资料

isEmpty
```
public static boolean isEmpty(String str)
```
Checks if a String is empty ("") or null.
```
 StringUtils.isEmpty(null)      = true
 StringUtils.isEmpty("")        = true
 StringUtils.isEmpty(" ")       = false
 StringUtils.isEmpty("bob")     = false
 StringUtils.isEmpty("  bob  ") = false
 
```
NOTE: This method changed in Lang version 2.0. It no longer trims the String. That functionality is available in isBlank().
参数:

str - the String to check, may be null

返回:

true if the String is empty or null

isNotEmpty

public static boolean isNotEmpty(String str)

Checks if a String is not empty ("") and not null.

 StringUtils.isNotEmpty(null)      = false
 StringUtils.isNotEmpty("")        = false
 StringUtils.isNotEmpty(" ")       = true
 StringUtils.isNotEmpty("bob")     = true
 StringUtils.isNotEmpty("  bob  ") = true

参数:: str - the String to check, may be null
返回:: true if the String is not empty and not null

isBlank

public static boolean isBlank(String str)

Checks if a String is whitespace, empty ("") or null.

 StringUtils.isBlank(null)      = true
 StringUtils.isBlank("null")      = true
 StringUtils.isBlank("")        = true
 StringUtils.isBlank(" ")       = true
 StringUtils.isBlank("bob")     = false
 StringUtils.isBlank("  bob  ") = false

参数:: str - the String to check, may be null
返回:: true if the String is null, empty or whitespace
从以下版本开始:: 2.0

isNotBlank

public static boolean isNotBlank(String str)

Checks if a String is not empty (""), not null and not whitespace only.

 StringUtils.isNotBlank(null)      = false
 StringUtils.isNotBlank("null")    = false
 StringUtils.isNotBlank("")        = false
 StringUtils.isNotBlank(" ")       = false
 StringUtils.isNotBlank("bob")     = true
 StringUtils.isNotBlank("  bob  ") = true

参数:: str - the String to check, may be null
返回:: true if the String is not empty and not null and not whitespace
从以下版本开始:: 2.0

clean
```
public static String clean(String str)
```
已过时。 Use the clearer named trimToEmpty(String). Method will be removed in Commons Lang 3.0.
Removes control characters (char <= 32) from both ends of this String, handling null by returning an empty String ("").
```
 StringUtils.clean(null)          = ""
 StringUtils.clean("")            = ""
 StringUtils.clean("abc")         = "abc"
 StringUtils.clean("    abc    ") = "abc"
 StringUtils.clean("     ")       = ""
 
```
参数:

str - the String to clean, may be null

返回:

the trimmed text, never null

另请参阅:

String.trim()

trim
```
public static String trim(String str)
```
Removes control characters (char <= 32) from both ends of this String, handling null by returning null.

The String is trimmed using String.trim(). Trim removes start and end characters <= 32. To strip whitespace use strip(String).

To trim your choice of characters, use the strip(String, String) methods.
```
 StringUtils.trim(null)          = null
 StringUtils.trim("")            = ""
 StringUtils.trim("     ")       = ""
 StringUtils.trim("abc")         = "abc"
 StringUtils.trim("    abc    ") = "abc"
 
```
参数:

str - the String to be trimmed, may be null

返回:

the trimmed string, null if null String input

trimToNull
```
public static String trimToNull(String str)
```
Removes control characters (char <= 32) from both ends of this String returning null if the String is empty ("") after the trim or if it is null.
The String is trimmed using String.trim(). Trim removes start and end characters <= 32. To strip whitespace use stripToNull(String).
```
 StringUtils.trimToNull(null)          = null
 StringUtils.trimToNull("")            = null
 StringUtils.trimToNull("     ")       = null
 StringUtils.trimToNull("abc")         = "abc"
 StringUtils.trimToNull("    abc    ") = "abc"
 
```
参数:

str - the String to be trimmed, may be null

返回:

the trimmed String, null if only chars <= 32, empty or null String input

从以下版本开始:

2.0

trimToEmpty
```
public static String trimToEmpty(String str)
```
Removes control characters (char <= 32) from both ends of this String returning an empty String ("") if the String is empty ("") after the trim or if it is null.
The String is trimmed using String.trim(). Trim removes start and end characters <= 32. To strip whitespace use stripToEmpty(String).
```
 StringUtils.trimToEmpty(null)          = ""
 StringUtils.trimToEmpty("")            = ""
 StringUtils.trimToEmpty("     ")       = ""
 StringUtils.trimToEmpty("abc")         = "abc"
 StringUtils.trimToEmpty("    abc    ") = "abc"
 
```
参数:

str - the String to be trimmed, may be null

返回:

the trimmed String, or an empty String if null input

从以下版本开始:

2.0

strip

public static String strip(String str)

Strips whitespace from the start and end of a String.

This is similar to trim(String) but removes whitespace. Whitespace is defined by Character.isWhitespace(char).

A null input String returns null.

 StringUtils.strip(null)     = null
 StringUtils.strip("")       = ""
 StringUtils.strip("   ")    = ""
 StringUtils.strip("abc")    = "abc"
 StringUtils.strip("  abc")  = "abc"
 StringUtils.strip("abc  ")  = "abc"
 StringUtils.strip(" abc ")  = "abc"
 StringUtils.strip(" ab c ") = "ab c"

参数:: str - the String to remove whitespace from, may be null
返回:: the stripped String, null if null String input

stripToNull

public static String stripToNull(String str)

Strips whitespace from the start and end of a String returning null if the String is empty ("") after the strip.

This is similar to trimToNull(String) but removes whitespace. Whitespace is defined by Character.isWhitespace(char).

 StringUtils.stripToNull(null)     = null
 StringUtils.stripToNull("")       = null
 StringUtils.stripToNull("   ")    = null
 StringUtils.stripToNull("abc")    = "abc"
 StringUtils.stripToNull("  abc")  = "abc"
 StringUtils.stripToNull("abc  ")  = "abc"
 StringUtils.stripToNull(" abc ")  = "abc"
 StringUtils.stripToNull(" ab c ") = "ab c"

参数:: str - the String to be stripped, may be null
返回:: the stripped String, null if whitespace, empty or null String input
从以下版本开始:: 2.0

stripToEmpty

public static String stripToEmpty(String str)

Strips whitespace from the start and end of a String returning an empty String if null input.

This is similar to trimToEmpty(String) but removes whitespace. Whitespace is defined by Character.isWhitespace(char).

 StringUtils.stripToEmpty(null)     = ""
 StringUtils.stripToEmpty("")       = ""
 StringUtils.stripToEmpty("   ")    = ""
 StringUtils.stripToEmpty("abc")    = "abc"
 StringUtils.stripToEmpty("  abc")  = "abc"
 StringUtils.stripToEmpty("abc  ")  = "abc"
 StringUtils.stripToEmpty(" abc ")  = "abc"
 StringUtils.stripToEmpty(" ab c ") = "ab c"

参数:: str - the String to be stripped, may be null
返回:: the trimmed String, or an empty String if null input
从以下版本开始:: 2.0

strip
```
public static String strip(String str,
                           String stripChars)
```
Strips any of a set of characters from the start and end of a String. This is similar to String.trim() but allows the characters to be stripped to be controlled.

A null input String returns null. An empty string ("") input returns the empty string.

If the stripChars String is null, whitespace is stripped as defined by Character.isWhitespace(char). Alternatively use strip(String).
```
 StringUtils.strip(null, *)          = null
 StringUtils.strip("", *)            = ""
 StringUtils.strip("abc", null)      = "abc"
 StringUtils.strip("  abc", null)    = "abc"
 StringUtils.strip("abc  ", null)    = "abc"
 StringUtils.strip(" abc ", null)    = "abc"
 StringUtils.strip("  abcyx", "xyz") = "  abc"
 
```
参数:

str - the String to remove characters from, may be null

stripChars - the characters to remove, null treated as whitespace

返回:

the stripped String, null if null String input

stripStart

public static String stripStart(String str,
                                String stripChars)

Strips any of a set of characters from the start of a String.

A null input String returns null. An empty string ("") input returns the empty string.

If the stripChars String is null, whitespace is stripped as defined by Character.isWhitespace(char).

 StringUtils.stripStart(null, *)          = null
 StringUtils.stripStart("", *)            = ""
 StringUtils.stripStart("abc", "")        = "abc"
 StringUtils.stripStart("abc", null)      = "abc"
 StringUtils.stripStart("  abc", null)    = "abc"
 StringUtils.stripStart("abc  ", null)    = "abc  "
 StringUtils.stripStart(" abc ", null)    = "abc "
 StringUtils.stripStart("yxabc  ", "xyz") = "abc  "

参数:: str - the String to remove characters from, may be null; stripChars - the characters to remove, null treated as whitespace
返回:: the stripped String, null if null String input

stripEnd

public static String stripEnd(String str,
                              String stripChars)

Strips any of a set of characters from the end of a String.

A null input String returns null. An empty string ("") input returns the empty string.

If the stripChars String is null, whitespace is stripped as defined by Character.isWhitespace(char).

 StringUtils.stripEnd(null, *)          = null
 StringUtils.stripEnd("", *)            = ""
 StringUtils.stripEnd("abc", "")        = "abc"
 StringUtils.stripEnd("abc", null)      = "abc"
 StringUtils.stripEnd("  abc", null)    = "  abc"
 StringUtils.stripEnd("abc  ", null)    = "abc"
 StringUtils.stripEnd(" abc ", null)    = " abc"
 StringUtils.stripEnd("  abcyx", "xyz") = "  abc"
 StringUtils.stripEnd("120.00", ".0")   = "12"

参数:: str - the String to remove characters from, may be null; stripChars - the set of characters to remove, null treated as whitespace
返回:: the stripped String, null if null String input

stripAll
```
public static String[] stripAll(String[] strs)
```
Strips whitespace from the start and end of every String in an array. Whitespace is defined by Character.isWhitespace(char).

A new array is returned each time, except for length zero. A null array will return null. An empty array will return itself. A null array entry will be ignored.
```
 StringUtils.stripAll(null)             = null
 StringUtils.stripAll([])               = []
 StringUtils.stripAll(["abc", "  abc"]) = ["abc", "abc"]
 StringUtils.stripAll(["abc  ", null])  = ["abc", null]
 
```
参数:

strs - the array to remove whitespace from, may be null

返回:

the stripped Strings, null if null array input

stripAll
```
public static String[] stripAll(String[] strs,
                                String stripChars)
```
Strips any of a set of characters from the start and end of every String in an array.
Whitespace is defined by Character.isWhitespace(char).

A new array is returned each time, except for length zero. A null array will return null. An empty array will return itself. A null array entry will be ignored. A null stripChars will strip whitespace as defined by Character.isWhitespace(char).
```
 StringUtils.stripAll(null, *)                = null
 StringUtils.stripAll([], *)                  = []
 StringUtils.stripAll(["abc", "  abc"], null) = ["abc", "abc"]
 StringUtils.stripAll(["abc  ", null], null)  = ["abc", null]
 StringUtils.stripAll(["abc  ", null], "yz")  = ["abc  ", null]
 StringUtils.stripAll(["yabcz", null], "yz")  = ["abc", null]
 
```
参数:

strs - the array to remove characters from, may be null

stripChars - the characters to remove, null treated as whitespace

返回:

the stripped Strings, null if null array input

equals
```
public static boolean equals(String str1,
                             String str2)
```
Compares two Strings, returning true if they are equal.

nulls are handled without exceptions. Two null references are considered to be equal. The comparison is case sensitive.
```
 StringUtils.equals(null, null)   = true
 StringUtils.equals(null, "abc")  = false
 StringUtils.equals("abc", null)  = false
 StringUtils.equals("abc", "abc") = true
 StringUtils.equals("abc", "ABC") = false
 
```
参数:

str1 - the first String, may be null

str2 - the second String, may be null

返回:

true if the Strings are equal, case sensitive, or both null

另请参阅:

String.equals(Object)

equalsIgnoreCase

public static boolean equalsIgnoreCase(String str1,
                                       String str2)

Compares two Strings, returning true if they are equal ignoring the case.

nulls are handled without exceptions. Two null references are considered equal. Comparison is case insensitive.

 StringUtils.equalsIgnoreCase(null, null)   = true
 StringUtils.equalsIgnoreCase(null, "abc")  = false
 StringUtils.equalsIgnoreCase("abc", null)  = false
 StringUtils.equalsIgnoreCase("abc", "abc") = true
 StringUtils.equalsIgnoreCase("abc", "ABC") = true

参数:: str1 - the first String, may be null; str2 - the second String, may be null
返回:: true if the Strings are equal, case insensitive, or both null
另请参阅:: String.equalsIgnoreCase(String)

indexOf
```
public static int indexOf(String str,
                          char searchChar)
```
Finds the first index within a String, handling null. This method uses String.indexOf(int).

A null or empty ("") String will return INDEX_NOT_FOUND (-1).
```
 StringUtils.indexOf(null, *)         = -1
 StringUtils.indexOf("", *)           = -1
 StringUtils.indexOf("aabaabaa", 'a') = 0
 StringUtils.indexOf("aabaabaa", 'b') = 2
 
```
参数:

str - the String to check, may be null

searchChar - the character to find

返回:

the first index of the search character, -1 if no match or null string input

从以下版本开始:

2.0

indexOf
```
public static int indexOf(String str,
                          char searchChar,
                          int startPos)
```
Finds the first index within a String from a start position, handling null. This method uses String.indexOf(int, int).

A null or empty ("") String will return (INDEX_NOT_FOUND) -1. A negative start position is treated as zero. A start position greater than the string length returns -1.
```
 StringUtils.indexOf(null, *, *)          = -1
 StringUtils.indexOf("", *, *)            = -1
 StringUtils.indexOf("aabaabaa", 'b', 0)  = 2
 StringUtils.indexOf("aabaabaa", 'b', 3)  = 5
 StringUtils.indexOf("aabaabaa", 'b', 9)  = -1
 StringUtils.indexOf("aabaabaa", 'b', -1) = 2
 
```
参数:

str - the String to check, may be null

searchChar - the character to find

startPos - the start position, negative treated as zero

返回:

the first index of the search character, -1 if no match or null string input

从以下版本开始:

2.0

indexOf

public static int indexOf(String str,
                          String searchStr)

Finds the first index within a String, handling null. This method uses String.indexOf(String).

A null String will return -1.

 StringUtils.indexOf(null, *)          = -1
 StringUtils.indexOf(*, null)          = -1
 StringUtils.indexOf("", "")           = 0
 StringUtils.indexOf("", *)            = -1 (except when * = "")
 StringUtils.indexOf("aabaabaa", "a")  = 0
 StringUtils.indexOf("aabaabaa", "b")  = 2
 StringUtils.indexOf("aabaabaa", "ab") = 1
 StringUtils.indexOf("aabaabaa", "")   = 0

参数:: str - the String to check, may be null; searchStr - the String to find, may be null
返回:: the first index of the search String, -1 if no match or null string input
从以下版本开始:: 2.0

ordinalIndexOf

public static int ordinalIndexOf(String str,
                                 String searchStr,
                                 int ordinal)

Finds the n-th index within a String, handling null. This method uses String.indexOf(String).

A null String will return -1.

 StringUtils.ordinalIndexOf(null, *, *)          = -1
 StringUtils.ordinalIndexOf(*, null, *)          = -1
 StringUtils.ordinalIndexOf("", "", *)           = 0
 StringUtils.ordinalIndexOf("aabaabaa", "a", 1)  = 0
 StringUtils.ordinalIndexOf("aabaabaa", "a", 2)  = 1
 StringUtils.ordinalIndexOf("aabaabaa", "b", 1)  = 2
 StringUtils.ordinalIndexOf("aabaabaa", "b", 2)  = 5
 StringUtils.ordinalIndexOf("aabaabaa", "ab", 1) = 1
 StringUtils.ordinalIndexOf("aabaabaa", "ab", 2) = 4
 StringUtils.ordinalIndexOf("aabaabaa", "", 1)   = 0
 StringUtils.ordinalIndexOf("aabaabaa", "", 2)   = 0

Note that 'head(String str, int n)' may be implemented as:

   str.substring(0, lastOrdinalIndexOf(str, "\n", n))

参数:: str - the String to check, may be null; searchStr - the String to find, may be null; ordinal - the n-th searchStr to find
返回:: the n-th index of the search String, -1 (INDEX_NOT_FOUND) if no match or null string input
从以下版本开始:: 2.1

ordinalIndexOf
```
private static int ordinalIndexOf(String str,
                                  String searchStr,
                                  int ordinal,
                                  boolean lastIndex)
```
Finds the n-th index within a String, handling null. This method uses String.indexOf(String).

A null String will return -1.

参数:

str - the String to check, may be null

searchStr - the String to find, may be null

ordinal - the n-th searchStr to find

lastIndex - true if lastOrdinalIndexOf() otherwise false if ordinalIndexOf()

返回:

the n-th index of the search String, -1 (INDEX_NOT_FOUND) if no match or null string input

indexOf

public static int indexOf(String str,
                          String searchStr,
                          int startPos)

Finds the first index within a String, handling null. This method uses String.indexOf(String, int).

A null String will return -1. A negative start position is treated as zero. An empty ("") search String always matches. A start position greater than the string length only matches an empty search String.

 StringUtils.indexOf(null, *, *)          = -1
 StringUtils.indexOf(*, null, *)          = -1
 StringUtils.indexOf("", "", 0)           = 0
 StringUtils.indexOf("", *, 0)            = -1 (except when * = "")
 StringUtils.indexOf("aabaabaa", "a", 0)  = 0
 StringUtils.indexOf("aabaabaa", "b", 0)  = 2
 StringUtils.indexOf("aabaabaa", "ab", 0) = 1
 StringUtils.indexOf("aabaabaa", "b", 3)  = 5
 StringUtils.indexOf("aabaabaa", "b", 9)  = -1
 StringUtils.indexOf("aabaabaa", "b", -1) = 2
 StringUtils.indexOf("aabaabaa", "", 2)   = 2
 StringUtils.indexOf("abc", "", 9)        = 3

参数:: str - the String to check, may be null; searchStr - the String to find, may be null; startPos - the start position, negative treated as zero
返回:: the first index of the search String, -1 if no match or null string input
从以下版本开始:: 2.0

indexOfIgnoreCase

public static int indexOfIgnoreCase(String str,
                                    String searchStr)

Case in-sensitive find of the first index within a String.

 StringUtils.indexOfIgnoreCase(null, *)          = -1
 StringUtils.indexOfIgnoreCase(*, null)          = -1
 StringUtils.indexOfIgnoreCase("", "")           = 0
 StringUtils.indexOfIgnoreCase("aabaabaa", "a")  = 0
 StringUtils.indexOfIgnoreCase("aabaabaa", "b")  = 2
 StringUtils.indexOfIgnoreCase("aabaabaa", "ab") = 1

参数:: str - the String to check, may be null; searchStr - the String to find, may be null
返回:: the first index of the search String, -1 if no match or null string input
从以下版本开始:: 2.5

indexOfIgnoreCase

public static int indexOfIgnoreCase(String str,
                                    String searchStr,
                                    int startPos)

Case in-sensitive find of the first index within a String from the specified position.

 StringUtils.indexOfIgnoreCase(null, *, *)          = -1
 StringUtils.indexOfIgnoreCase(*, null, *)          = -1
 StringUtils.indexOfIgnoreCase("", "", 0)           = 0
 StringUtils.indexOfIgnoreCase("aabaabaa", "A", 0)  = 0
 StringUtils.indexOfIgnoreCase("aabaabaa", "B", 0)  = 2
 StringUtils.indexOfIgnoreCase("aabaabaa", "AB", 0) = 1
 StringUtils.indexOfIgnoreCase("aabaabaa", "B", 3)  = 5
 StringUtils.indexOfIgnoreCase("aabaabaa", "B", 9)  = -1
 StringUtils.indexOfIgnoreCase("aabaabaa", "B", -1) = 2
 StringUtils.indexOfIgnoreCase("aabaabaa", "", 2)   = 2
 StringUtils.indexOfIgnoreCase("abc", "", 9)        = 3

参数:: str - the String to check, may be null; searchStr - the String to find, may be null; startPos - the start position, negative treated as zero
返回:: the first index of the search String, -1 if no match or null string input
从以下版本开始:: 2.5

lastIndexOf
```
public static int lastIndexOf(String str,
                              char searchChar)
```
Finds the last index within a String, handling null. This method uses String.lastIndexOf(int).

A null or empty ("") String will return -1.
```
 StringUtils.lastIndexOf(null, *)         = -1
 StringUtils.lastIndexOf("", *)           = -1
 StringUtils.lastIndexOf("aabaabaa", 'a') = 7
 StringUtils.lastIndexOf("aabaabaa", 'b') = 5
 
```
参数:

str - the String to check, may be null

searchChar - the character to find

返回:

the last index of the search character, -1 if no match or null string input

从以下版本开始:

2.0

lastIndexOf

public static int lastIndexOf(String str,
                              char searchChar,
                              int startPos)

Finds the last index within a String from a start position, handling null. This method uses String.lastIndexOf(int, int).

A null or empty ("") String will return -1. A negative start position returns -1. A start position greater than the string length searches the whole string.

 StringUtils.lastIndexOf(null, *, *)          = -1
 StringUtils.lastIndexOf("", *,  *)           = -1
 StringUtils.lastIndexOf("aabaabaa", 'b', 8)  = 5
 StringUtils.lastIndexOf("aabaabaa", 'b', 4)  = 2
 StringUtils.lastIndexOf("aabaabaa", 'b', 0)  = -1
 StringUtils.lastIndexOf("aabaabaa", 'b', 9)  = 5
 StringUtils.lastIndexOf("aabaabaa", 'b', -1) = -1
 StringUtils.lastIndexOf("aabaabaa", 'a', 0)  = 0

参数:: str - the String to check, may be null; searchChar - the character to find; startPos - the start position
返回:: the last index of the search character, -1 if no match or null string input
从以下版本开始:: 2.0

lastIndexOf

public static int lastIndexOf(String str,
                              String searchStr)

Finds the last index within a String, handling null. This method uses String.lastIndexOf(String).

A null String will return -1.

 StringUtils.lastIndexOf(null, *)          = -1
 StringUtils.lastIndexOf(*, null)          = -1
 StringUtils.lastIndexOf("", "")           = 0
 StringUtils.lastIndexOf("aabaabaa", "a")  = 7
 StringUtils.lastIndexOf("aabaabaa", "b")  = 5
 StringUtils.lastIndexOf("aabaabaa", "ab") = 4
 StringUtils.lastIndexOf("aabaabaa", "")   = 8

参数:: str - the String to check, may be null; searchStr - the String to find, may be null
返回:: the last index of the search String, -1 if no match or null string input
从以下版本开始:: 2.0

lastOrdinalIndexOf

public static int lastOrdinalIndexOf(String str,
                                     String searchStr,
                                     int ordinal)

Finds the n-th last index within a String, handling null. This method uses String.lastIndexOf(String).

A null String will return -1.

 StringUtils.lastOrdinalIndexOf(null, *, *)          = -1
 StringUtils.lastOrdinalIndexOf(*, null, *)          = -1
 StringUtils.lastOrdinalIndexOf("", "", *)           = 0
 StringUtils.lastOrdinalIndexOf("aabaabaa", "a", 1)  = 7
 StringUtils.lastOrdinalIndexOf("aabaabaa", "a", 2)  = 6
 StringUtils.lastOrdinalIndexOf("aabaabaa", "b", 1)  = 5
 StringUtils.lastOrdinalIndexOf("aabaabaa", "b", 2)  = 2
 StringUtils.lastOrdinalIndexOf("aabaabaa", "ab", 1) = 4
 StringUtils.lastOrdinalIndexOf("aabaabaa", "ab", 2) = 1
 StringUtils.lastOrdinalIndexOf("aabaabaa", "", 1)   = 8
 StringUtils.lastOrdinalIndexOf("aabaabaa", "", 2)   = 8

Note that 'tail(String str, int n)' may be implemented as:

   str.substring(lastOrdinalIndexOf(str, "\n", n) + 1)

参数:: str - the String to check, may be null; searchStr - the String to find, may be null; ordinal - the n-th last searchStr to find
返回:: the n-th last index of the search String, -1 (INDEX_NOT_FOUND) if no match or null string input
从以下版本开始:: 2.5

lastIndexOf

public static int lastIndexOf(String str,
                              String searchStr,
                              int startPos)

Finds the first index within a String, handling null. This method uses String.lastIndexOf(String, int).

A null String will return -1. A negative start position returns -1. An empty ("") search String always matches unless the start position is negative. A start position greater than the string length searches the whole string.

 StringUtils.lastIndexOf(null, *, *)          = -1
 StringUtils.lastIndexOf(*, null, *)          = -1
 StringUtils.lastIndexOf("aabaabaa", "a", 8)  = 7
 StringUtils.lastIndexOf("aabaabaa", "b", 8)  = 5
 StringUtils.lastIndexOf("aabaabaa", "ab", 8) = 4
 StringUtils.lastIndexOf("aabaabaa", "b", 9)  = 5
 StringUtils.lastIndexOf("aabaabaa", "b", -1) = -1
 StringUtils.lastIndexOf("aabaabaa", "a", 0)  = 0
 StringUtils.lastIndexOf("aabaabaa", "b", 0)  = -1

参数:: str - the String to check, may be null; searchStr - the String to find, may be null; startPos - the start position, negative treated as zero
返回:: the first index of the search String, -1 if no match or null string input
从以下版本开始:: 2.0

lastIndexOfIgnoreCase
```
public static int lastIndexOfIgnoreCase(String str,
                                        String searchStr)
```
Case in-sensitive find of the last index within a String.

A null String will return -1. A negative start position returns -1. An empty ("") search String always matches unless the start position is negative. A start position greater than the string length searches the whole string.
```
 StringUtils.lastIndexOfIgnoreCase(null, *)          = -1
 StringUtils.lastIndexOfIgnoreCase(*, null)          = -1
 StringUtils.lastIndexOfIgnoreCase("aabaabaa", "A")  = 7
 StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B")  = 5
 StringUtils.lastIndexOfIgnoreCase("aabaabaa", "AB") = 4
 
```
参数:

str - the String to check, may be null

searchStr - the String to find, may be null

返回:

the first index of the search String, -1 if no match or null string input

从以下版本开始:

2.5

lastIndexOfIgnoreCase

public static int lastIndexOfIgnoreCase(String str,
                                        String searchStr,
                                        int startPos)

Case in-sensitive find of the last index within a String from the specified position.

 StringUtils.lastIndexOfIgnoreCase(null, *, *)          = -1
 StringUtils.lastIndexOfIgnoreCase(*, null, *)          = -1
 StringUtils.lastIndexOfIgnoreCase("aabaabaa", "A", 8)  = 7
 StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B", 8)  = 5
 StringUtils.lastIndexOfIgnoreCase("aabaabaa", "AB", 8) = 4
 StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B", 9)  = 5
 StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B", -1) = -1
 StringUtils.lastIndexOfIgnoreCase("aabaabaa", "A", 0)  = 0
 StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B", 0)  = -1

参数:: str - the String to check, may be null; searchStr - the String to find, may be null; startPos - the start position
返回:: the first index of the search String, -1 if no match or null string input
从以下版本开始:: 2.5

contains
```
public static boolean contains(String str,
                               char searchChar)
```
Checks if String contains a search character, handling null. This method uses String.indexOf(int).

A null or empty ("") String will return false.
```
 StringUtils.contains(null, *)    = false
 StringUtils.contains("", *)      = false
 StringUtils.contains("abc", 'a') = true
 StringUtils.contains("abc", 'z') = false
 
```
参数:

str - the String to check, may be null

searchChar - the character to find

返回:

true if the String contains the search character, false if not or null string input

从以下版本开始:

2.0

contains

public static boolean contains(String str,
                               String searchStr)

Checks if String contains a search String, handling null. This method uses String.indexOf(String).

A null String will return false.

 StringUtils.contains(null, *)     = false
 StringUtils.contains(*, null)     = false
 StringUtils.contains("", "")      = true
 StringUtils.contains("abc", "")   = true
 StringUtils.contains("abc", "a")  = true
 StringUtils.contains("abc", "z")  = false

参数:: str - the String to check, may be null; searchStr - the String to find, may be null
返回:: true if the String contains the search String, false if not or null string input
从以下版本开始:: 2.0

containsIgnoreCase

public static boolean containsIgnoreCase(String str,
                                         String searchStr)

Checks if String contains a search String irrespective of case, handling null. Case-insensitivity is defined as by String.equalsIgnoreCase(String).

A null String will return false.

 StringUtils.contains(null, *) = false
 StringUtils.contains(*, null) = false
 StringUtils.contains("", "") = true
 StringUtils.contains("abc", "") = true
 StringUtils.contains("abc", "a") = true
 StringUtils.contains("abc", "z") = false
 StringUtils.contains("abc", "A") = true
 StringUtils.contains("abc", "Z") = false

参数:: str - the String to check, may be null; searchStr - the String to find, may be null
返回:: true if the String contains the search String irrespective of case or false if not or null string input

indexOfAny

public static int indexOfAny(String str,
                             String[] searchStrs)

Find the first index of any of a set of potential substrings.

A null String will return -1. A null or zero length search array will return -1. A null search array entry will be ignored, but a search array containing "" will return 0 if str is not null. This method uses String.indexOf(String).

 StringUtils.indexOfAny(null, *)                     = -1
 StringUtils.indexOfAny(*, null)                     = -1
 StringUtils.indexOfAny(*, [])                       = -1
 StringUtils.indexOfAny("zzabyycdxx", ["ab","cd"])   = 2
 StringUtils.indexOfAny("zzabyycdxx", ["cd","ab"])   = 2
 StringUtils.indexOfAny("zzabyycdxx", ["mn","op"])   = -1
 StringUtils.indexOfAny("zzabyycdxx", ["zab","aby"]) = 1
 StringUtils.indexOfAny("zzabyycdxx", [""])          = 0
 StringUtils.indexOfAny("", [""])                    = 0
 StringUtils.indexOfAny("", ["a"])                   = -1

参数:: str - the String to check, may be null; searchStrs - the Strings to search for, may be null
返回:: the first index of any of the searchStrs in str, -1 if no match

lastIndexOfAny

public static int lastIndexOfAny(String str,
                                 String[] searchStrs)

Find the latest index of any of a set of potential substrings.

A null String will return -1. A null search array will return -1. A null or zero length search array entry will be ignored, but a search array containing "" will return the length of str if str is not null. This method uses String.indexOf(String)

 StringUtils.lastIndexOfAny(null, *)                   = -1
 StringUtils.lastIndexOfAny(*, null)                   = -1
 StringUtils.lastIndexOfAny(*, [])                     = -1
 StringUtils.lastIndexOfAny(*, [null])                 = -1
 StringUtils.lastIndexOfAny("zzabyycdxx", ["ab","cd"]) = 6
 StringUtils.lastIndexOfAny("zzabyycdxx", ["cd","ab"]) = 6
 StringUtils.lastIndexOfAny("zzabyycdxx", ["mn","op"]) = -1
 StringUtils.lastIndexOfAny("zzabyycdxx", ["mn","op"]) = -1
 StringUtils.lastIndexOfAny("zzabyycdxx", ["mn",""])   = 10

参数:: str - the String to check, may be null; searchStrs - the Strings to search for, may be null
返回:: the last index of any of the Strings, -1 if no match

substring
```
public static String substring(String str,
                               int start)
```
Gets a substring from the specified String avoiding exceptions.

A negative start position can be used to start n characters from the end of the String.

A null String will return null. An empty ("") String will return "".
```
 StringUtils.substring(null, *)   = null
 StringUtils.substring("", *)     = ""
 StringUtils.substring("abc", 0)  = "abc"
 StringUtils.substring("abc", 2)  = "c"
 StringUtils.substring("abc", 4)  = ""
 StringUtils.substring("abc", -2) = "bc"
 StringUtils.substring("abc", -4) = "abc"
 
```
参数:

str - the String to get the substring from, may be null

start - the position to start from, negative means count back from the end of the String by this many characters

返回:

substring from start position, null if null String input

substring
```
public static String substring(String str,
                               int start,
                               int end)
```
Gets a substring from the specified String avoiding exceptions.

A negative start position can be used to start/end n characters from the end of the String.

The returned substring starts with the character in the start position and ends before the end position. All position counting is zero-based -- i.e., to start at the beginning of the string use start = 0. Negative start and end positions can be used to specify offsets relative to the end of the String.

If start is not strictly to the left of end, "" is returned.
```
 StringUtils.substring(null, *, *)    = null
 StringUtils.substring("", * ,  *)    = "";
 StringUtils.substring("abc", 0, 2)   = "ab"
 StringUtils.substring("abc", 2, 0)   = ""
 StringUtils.substring("abc", 2, 4)   = "c"
 StringUtils.substring("abc", 4, 6)   = ""
 StringUtils.substring("abc", 2, 2)   = ""
 StringUtils.substring("abc", -2, -1) = "b"
 StringUtils.substring("abc", -4, 2)  = "ab"
 
```
参数:

str - the String to get the substring from, may be null

start - the position to start from, negative means count back from the end of the String by this many characters

end - the position to end at (exclusive), negative means count back from the end of the String by this many characters

返回:

substring from start position to end positon, null if null String input

left
```
public static String left(String str,
                          int len)
```
Gets the leftmost len characters of a String.

If len characters are not available, or the String is null, the String will be returned without an exception. An empty String is returned if len is negative.
```
 StringUtils.left(null, *)    = null
 StringUtils.left(*, -ve)     = ""
 StringUtils.left("", *)      = ""
 StringUtils.left("abc", 0)   = ""
 StringUtils.left("abc", 2)   = "ab"
 StringUtils.left("abc", 4)   = "abc"
 
```
参数:

str - the String to get the leftmost characters from, may be null

len - the length of the required String

返回:

the leftmost characters, null if null String input

right
```
public static String right(String str,
                           int len)
```
Gets the rightmost len characters of a String.

If len characters are not available, or the String is null, the String will be returned without an an exception. An empty String is returned if len is negative.
```
 StringUtils.right(null, *)    = null
 StringUtils.right(*, -ve)     = ""
 StringUtils.right("", *)      = ""
 StringUtils.right("abc", 0)   = ""
 StringUtils.right("abc", 2)   = "bc"
 StringUtils.right("abc", 4)   = "abc"
 
```
参数:

str - the String to get the rightmost characters from, may be null

len - the length of the required String

返回:

the rightmost characters, null if null String input

mid
```
public static String mid(String str,
                         int pos,
                         int len)
```
Gets len characters from the middle of a String.

If len characters are not available, the remainder of the String will be returned without an exception. If the String is null, null will be returned. An empty String is returned if len is negative or exceeds the length of str.
```
 StringUtils.mid(null, *, *)    = null
 StringUtils.mid(*, *, -ve)     = ""
 StringUtils.mid("", 0, *)      = ""
 StringUtils.mid("abc", 0, 2)   = "ab"
 StringUtils.mid("abc", 0, 4)   = "abc"
 StringUtils.mid("abc", 2, 4)   = "c"
 StringUtils.mid("abc", 4, 2)   = ""
 StringUtils.mid("abc", -2, 2)  = "ab"
 
```
参数:

str - the String to get the characters from, may be null

pos - the position to start from, negative treated as zero

len - the length of the required String

返回:

the middle characters, null if null String input

substringBefore

public static String substringBefore(String str,
                                     String separator)

Gets the substring before the first occurrence of a separator. The separator is not returned.

A null string input will return null. An empty ("") string input will return the empty string. A null separator will return the input string.

If nothing is found, the string input is returned.

 StringUtils.substringBefore(null, *)      = null
 StringUtils.substringBefore("", *)        = ""
 StringUtils.substringBefore("abc", "a")   = ""
 StringUtils.substringBefore("abcba", "b") = "a"
 StringUtils.substringBefore("abc", "c")   = "ab"
 StringUtils.substringBefore("abc", "d")   = "abc"
 StringUtils.substringBefore("abc", "")    = ""
 StringUtils.substringBefore("abc", null)  = "abc"

参数:: str - the String to get a substring from, may be null; separator - the String to search for, may be null
返回:: the substring before the first occurrence of the separator, null if null String input
从以下版本开始:: 2.0

substringAfter
```
public static String substringAfter(String str,
                                    String separator)
```
Gets the substring after the first occurrence of a separator. The separator is not returned.

A null string input will return null. An empty ("") string input will return the empty string. A null separator will return the empty string if the input string is not null.

If nothing is found, the empty string is returned.
```
 StringUtils.substringAfter(null, *)      = null
 StringUtils.substringAfter("", *)        = ""
 StringUtils.substringAfter(*, null)      = ""
 StringUtils.substringAfter("abc", "a")   = "bc"
 StringUtils.substringAfter("abcba", "b") = "cba"
 StringUtils.substringAfter("abc", "c")   = ""
 StringUtils.substringAfter("abc", "d")   = ""
 StringUtils.substringAfter("abc", "")    = "abc"
 
```
参数:

str - the String to get a substring from, may be null

separator - the String to search for, may be null

返回:

the substring after the first occurrence of the separator, null if null String input

从以下版本开始:

2.0

substringBeforeLast

public static String substringBeforeLast(String str,
                                         String separator)

Gets the substring before the last occurrence of a separator. The separator is not returned.

A null string input will return null. An empty ("") string input will return the empty string. An empty or null separator will return the input string.

If nothing is found, the string input is returned.

 StringUtils.substringBeforeLast(null, *)      = null
 StringUtils.substringBeforeLast("", *)        = ""
 StringUtils.substringBeforeLast("abcba", "b") = "abc"
 StringUtils.substringBeforeLast("abc", "c")   = "ab"
 StringUtils.substringBeforeLast("a", "a")     = ""
 StringUtils.substringBeforeLast("a", "z")     = "a"
 StringUtils.substringBeforeLast("a", null)    = "a"
 StringUtils.substringBeforeLast("a", "")      = "a"

参数:: str - the String to get a substring from, may be null; separator - the String to search for, may be null
返回:: the substring before the last occurrence of the separator, null if null String input
从以下版本开始:: 2.0

substringAfterLast

public static String substringAfterLast(String str,
                                        String separator)

Gets the substring after the last occurrence of a separator. The separator is not returned.

A null string input will return null. An empty ("") string input will return the empty string. An empty or null separator will return the empty string if the input string is not null.

If nothing is found, the empty string is returned.

 StringUtils.substringAfterLast(null, *)      = null
 StringUtils.substringAfterLast("", *)        = ""
 StringUtils.substringAfterLast(*, "")        = ""
 StringUtils.substringAfterLast(*, null)      = ""
 StringUtils.substringAfterLast("abc", "a")   = "bc"
 StringUtils.substringAfterLast("abcba", "b") = "a"
 StringUtils.substringAfterLast("abc", "c")   = ""
 StringUtils.substringAfterLast("a", "a")     = ""
 StringUtils.substringAfterLast("a", "z")     = ""

参数:: str - the String to get a substring from, may be null; separator - the String to search for, may be null
返回:: the substring after the last occurrence of the separator, null if null String input
从以下版本开始:: 2.0

substringBetween

public static String substringBetween(String str,
                                      String tag)

Gets the String that is nested in between two instances of the same String.

A null input String returns null. A null tag returns null.

 StringUtils.substringBetween(null, *)            = null
 StringUtils.substringBetween("", "")             = ""
 StringUtils.substringBetween("", "tag")          = null
 StringUtils.substringBetween("tagabctag", null)  = null
 StringUtils.substringBetween("tagabctag", "")    = ""
 StringUtils.substringBetween("tagabctag", "tag") = "abc"

参数:: str - the String containing the substring, may be null; tag - the String before and after the substring, may be null
返回:: the substring, null if no match
从以下版本开始:: 2.0

substringBetween

public static String substringBetween(String str,
                                      String open,
                                      String close)

Gets the String that is nested in between two Strings. Only the first match is returned.

A null input String returns null. A null open/close returns null (no match). An empty ("") open and close returns an empty string.

 StringUtils.substringBetween("wx[b]yz", "[", "]") = "b"
 StringUtils.substringBetween(null, *, *)          = null
 StringUtils.substringBetween(*, null, *)          = null
 StringUtils.substringBetween(*, *, null)          = null
 StringUtils.substringBetween("", "", "")          = ""
 StringUtils.substringBetween("", "", "]")         = null
 StringUtils.substringBetween("", "[", "]")        = null
 StringUtils.substringBetween("yabcz", "", "")     = ""
 StringUtils.substringBetween("yabcz", "y", "z")   = "abc"
 StringUtils.substringBetween("yabczyabcz", "y", "z")   = "abc"

参数:: str - the String containing the substring, may be null; open - the String before the substring, may be null; close - the String after the substring, may be null
返回:: the substring, null if no match
从以下版本开始:: 2.0

类 StringUtils

字段概要

构造器概要

方法概要

从类继承的方法 java.lang.Object

字段详细资料

EMPTY

INDEX_NOT_FOUND

PAD_LIMIT

构造器详细资料

StringUtils

方法详细资料

isEmpty

isNotEmpty

isBlank

isNotBlank

clean

trim

trimToNull

trimToEmpty

strip

stripToNull

stripToEmpty

strip

stripStart

stripEnd

stripAll

stripAll

equals

equalsIgnoreCase

indexOf

indexOf

indexOf

ordinalIndexOf

ordinalIndexOf

indexOf

indexOfIgnoreCase

indexOfIgnoreCase

lastIndexOf

lastIndexOf

lastIndexOf

lastOrdinalIndexOf

lastIndexOf

lastIndexOfIgnoreCase

lastIndexOfIgnoreCase

contains

contains

containsIgnoreCase

indexOfAny

lastIndexOfAny

substring

substring

left

right

mid

substringBefore

substringAfter

substringBeforeLast

substringAfterLast

substringBetween

substringBetween