org.apache.commons.lang

Operations on arrays, primitive arrays (like int[]) and primitive wrapper arrays (like Integer[]).

This class tries to handle null input gracefully. An exception will not be thrown for a null array input.

Operations on bit-mapped fields.

Operations on boolean primitives and Boolean objects.

This class tries to handle null input gracefully.

Character encoding names required of every implementation of the Java platform.

According to JRE character encoding names:

Every implementation of the Java platform is required to support the following character encodings.

Operations on CharSets.

This class handles null input gracefully.

Operations on char primitives and Character objects.

This class tries to handle null input gracefully.

Operates on classes without using reflection.

This class handles invalid null inputs as best it can.

Provides HTML and XML entity utilities.

Thrown when an object is an instance of an unexpected type (a class or interface). This exception supplements the standard IllegalArgumentException by providing a more semantically rich description of the problem.

IllegalClassException represents the case where a method takes in a genericly typed parameter like Object (typically because it has to due to some other interface it implements), but this implementation only actually accepts a specific type, for example String.

Thrown to indicate an incomplete argument to a method.

A hash map that uses primitive ints for the key rather than objects.

Note that this class is for internal optimization purposes only, and may not be supported in future releases of Apache Commons Lang.

Operations to assist when working with a Locale .

This class tries to handle null input gracefully.

Thrown to indicate that a block of code has not been implemented.

Thrown to indicate that an argument was null and should not have been.

Represents a range of Number objects.

This class uses double comparisons.

Operations on Object.

This class tries to handle null input gracefully. An exception will generally not be thrown for a null input. Each method documents its behaviour in more detail.

Operations for random Strings.

Currently private high surrogate characters are ignored.

Assists with the serialization process and performs additional functionality based on serialization.

• Deep clone using serialization
• Serialize managing finally and IOException
• Deserialize managing finally and IOException

This class throws exceptions for invalid null inputs. Each method documents its behaviour in more detail.

Operations on java.lang.String that are null safe.

• IsEmpty/IsBlank - checks if a String contains text
• Trim/Strip - removes leading and trailing whitespace
• Equals - 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
• 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
• Reverse/ReverseDelimited - reverses a String
• Abbreviate - abbreviates a string using ellipsis
• Difference - compares Strings and reports on their differences
• LevensteinDistance - 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

StringUtils handles null input Strings quietly. That is to say that a null input will return null. Where a boolean or int is being returned details vary by method.

A side effect of the null handling is that a NullPointerException should be considered a bug in StringUtils (except for deprecated methods).

Methods in this class give sample code to explain their operation. The symbol * is used to indicate any input including null.

Thrown when it is impossible or undesirable to consume or throw a checked exception.

UnhandledException represents the case where a method has to deal with a checked exception but does not wish to.

Assists in validating arguments.

The class is based along the lines of JUnit.

Operations on Strings that contain words.

This class tries to handle null input gracefully. An exception will not be thrown for a null input. Each method documents its behaviour in more detail.