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com.google.common.base
Class Splitter

java.lang.Object
  extended by com.google.common.base.Splitter

public final class Splitter
extends Object

An object that divides strings (or other instances of CharSequence) into substrings, by recognizing a separator (a.k.a. "delimiter") which can be expressed as a single character, literal string, regular expression, CharMatcher, or by using a fixed substring length. This class provides the complementary functionality to Joiner.

Here is the most basic example of Splitter usage: 

   Splitter.on(',').split("foo,bar")
This invocation returns an Iterable<String> containing "foo" and "bar", in that order.

By default Splitter's behavior is very simplistic: 

   Splitter.on(',').split("foo,,bar,  quux")
This returns an iterable containing ["foo", "", "bar", " quux"]. Notice that the splitter does not assume that you want empty strings removed, or that you wish to trim whitespace. If you want features like these, simply ask for them: 
 private static final Splitter MY_SPLITTER = Splitter.on(',')
       .trimResults()
       .omitEmptyStrings();
Now MY_SPLITTER.split("foo, ,bar, quux,") returns an iterable containing just ["foo", "bar", "quux"]. Note that the order in which the configuration methods are called is never significant; for instance, trimming is always applied first before checking for an empty result, regardless of the order in which the trimResults() and omitEmptyStrings() methods were invoked.

Warning: splitter instances are always immutable; a configuration method such as omitEmptyStrings has no effect on the instance it is invoked on! You must store and use the new splitter instance returned by the method. This makes splitters thread-safe, and safe to store as static final constants (as illustrated above). 

   // Bad! Do not do this!
   Splitter splitter = Splitter.on('/');
   splitter.trimResults(); // does nothing!
   return splitter.split("wrong / wrong / wrong");
The separator recognized by the splitter does not have to be a single literal character as in the examples above. See the methods on(String), on(Pattern) and on(CharMatcher) for examples of other ways to specify separators.

Note: this class does not mimic any of the quirky behaviors of similar JDK methods; for instance, it does not silently discard trailing separators, as does String.split(String), nor does it have a default behavior of using five particular whitespace characters as separators, like StringTokenizer.

Since:
1
Author:
Julien Silland, Jesse Wilson, Kevin Bourrillion

Method Summary
static Splitter fixedLength(int length)
          Returns a splitter that divides strings into pieces of the given length.
 Splitter omitEmptyStrings()
          Returns a splitter that behaves equivalently to this splitter, but automatically omits empty strings from the results.
static Splitter on(char separator)
          Returns a splitter that uses the given single-character separator.
static Splitter on(CharMatcher separatorMatcher)
          Returns a splitter that considers any single character matched by the given CharMatcher to be a separator.
static Splitter on(Pattern separatorPattern)
          Returns a splitter that considers any subsequence matching pattern to be a separator.
static Splitter on(String separator)
          Returns a splitter that uses the given fixed string as a separator.
static Splitter onPattern(String separatorPattern)
          Returns a splitter that considers any subsequence matching a given pattern (regular expression) to be a separator.
 Iterable<String> split(CharSequence sequence)
          Splits the CharSequence passed in parameter.
 Splitter trimResults()
          Returns a splitter that behaves equivalently to this splitter, but automatically removes leading and trailing whitespace from each returned substring; equivalent to trimResults(CharMatcher.WHITESPACE).
 Splitter trimResults(CharMatcher trimmer)
          Returns a splitter that behaves equivalently to this splitter, but removes all leading or trailing characters matching the given CharMatcher from each returned substring.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Method Detail

on

public static Splitter on(char separator)
Returns a splitter that uses the given single-character separator. For example, Splitter.on(',').split("foo,,bar") returns an iterable containing ["foo", "", "bar"].

Parameters:
separator - the character to recognize as a separator
Returns:
a splitter, with default settings, that recognizes that separator

on

public static Splitter on(CharMatcher separatorMatcher)
Returns a splitter that considers any single character matched by the given CharMatcher to be a separator. For example, Splitter.on(CharMatcher.anyOf(";,")).split("foo,;bar,quux") returns an iterable containing ["foo", "", "bar", "quux"].

Parameters:
separatorMatcher - a CharMatcher that determines whether a character is a separator
Returns:
a splitter, with default settings, that uses this matcher

on

public static Splitter on(String separator)
Returns a splitter that uses the given fixed string as a separator. For example, Splitter.on(", ").split("foo, bar, baz,qux") returns an iterable containing ["foo", "bar", "baz,qux"].

Parameters:
separator - the literal, nonempty string to recognize as a separator
Returns:
a splitter, with default settings, that recognizes that separator

on

public static Splitter on(Pattern separatorPattern)
Returns a splitter that considers any subsequence matching pattern to be a separator. For example, Splitter.on(Pattern.compile("\r?\n")).split(entireFile) splits a string into lines whether it uses DOS-style or UNIX-style line terminators.

Parameters:
separatorPattern - the pattern that determines whether a subsequence is a separator. This pattern may not match the empty string.
Returns:
a splitter, with default settings, that uses this pattern
Throws:
IllegalArgumentException - if separatorPattern matches the empty string

onPattern

public static Splitter onPattern(String separatorPattern)
Returns a splitter that considers any subsequence matching a given pattern (regular expression) to be a separator. For example, Splitter.onPattern("\r?\n").split(entireFile) splits a string into lines whether it uses DOS-style or UNIX-style line terminators. This is equivalent to Splitter.on(Pattern.compile(pattern)).

Parameters:
separatorPattern - the pattern that determines whether a subsequence is a separator. This pattern may not match the empty string.
Returns:
a splitter, with default settings, that uses this pattern
Throws:
PatternSyntaxException - if separatorPattern is a malformed expression
IllegalArgumentException - if separatorPattern matches the empty string

fixedLength

public static Splitter fixedLength(int length)
Returns a splitter that divides strings into pieces of the given length. For example, Splitter.fixedLength(2).split("abcde") returns an iterable containing ["ab", "cd", "e"]. The last piece can be smaller than length but will never be empty.

Parameters:
length - the desired length of pieces after splitting
Returns:
a splitter, with default settings, that can split into fixed sized pieces

omitEmptyStrings

public Splitter omitEmptyStrings()
Returns a splitter that behaves equivalently to this splitter, but automatically omits empty strings from the results. For example, Splitter.on(',').omitEmptyStrings().split(",a,,,b,c,,") returns an iterable containing only ["a", "b", "c"].

If either trimResults option is also specified when creating a splitter, that splitter always trims results first before checking for emptiness. So, for example, Splitter.on(':').omitEmptyStrings().trimResults().split(": : : ") returns an empty iterable.

Note that it is ordinarily not possible for split(CharSequence) to return an empty iterable, but when using this option, it can (if the input sequence consists of nothing but separators).

Returns:
a splitter with the desired configuration

trimResults

public Splitter trimResults()
Returns a splitter that behaves equivalently to this splitter, but automatically removes leading and trailing whitespace from each returned substring; equivalent to trimResults(CharMatcher.WHITESPACE). For example, Splitter.on(',').trimResults().split(" a, b ,c ") returns an iterable containing ["a", "b", "c"].

Returns:
a splitter with the desired configuration

trimResults

public Splitter trimResults(CharMatcher trimmer)
Returns a splitter that behaves equivalently to this splitter, but removes all leading or trailing characters matching the given CharMatcher from each returned substring. For example, Splitter.on(',').trimResults(CharMatcher.is('_')).split("_a ,_b_ ,c__") returns an iterable containing ["a ", "b_ ", "c"].

Parameters:
trimmer - a CharMatcher that determines whether a character should be removed from the beginning/end of a subsequence
Returns:
a splitter with the desired configuration

split

public Iterable<String> split(CharSequence sequence)
Splits the CharSequence passed in parameter.

Parameters:
sequence - the sequence of characters to split
Returns:
an iteration over the segments split from the parameter.
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