.split()

The .split() method takes a string and splits it into an array of substrings based on a pattern delimiter. The pattern provided is a regular expression that will split the original string based on where the pattern is matched in the string.

The method will throw a PatternSyntaxException for a pattern that is an invalid regular expression.

Syntax

String[] result = string.split(delimiter, limit);

Where string is the string to be split, and delimiter is a string containing a regular expression pattern.

The optional limit parameter is an integer, and has the following behavior:

• limit > 0: .split() will return at most limit entries, stopping after limit-1 matches.
• limit < 0: .split() will match as many times as possible, resulting in an array of any size.
• limit = 0: .split() is the same as limit < 0 except that trailing empty strings will be discarded.

Example 1

The following uses the regular expression “\s+” which matches one or more whitespace characters.

public class Example{
  public static void main(String args[]){
    String words = "This  is  a    string    of  words.";
    String[] result = words.split("\\s+"); // Splits words on matching sequences of whitespace.
    for(String w:result){
      System.out.println(w);
    }
  }
}

This outputs the following:

This
is
a
string
of
words.

Example 2

This example uses the pattern “,\s*“ which matches a comma followed by zero or more whitespace characters, it also uses a limit parameter.

public class Example{
  public static void main(String args[]){
    String words = "This, is, a, comma,delimited, list, of, words";
    String[] result = words.split(",\\s*",6); // Splits words on matching commas followed by arbitrary whitespace.
    for(String w:result){
      System.out.println(w);
    }
  }
}

This outputs the following:

This
is
a
comma
delimited
list, of, words

Example 3

This example shows the difference between a negative limit and a limit of zero.

public class Example{
  public static void main(String args[]){
    String words = "This,string,has,extra,commas,,,,";
    String[] result1 = words.split(",",-2); // Split on each comma.
    String[] result2 = words.split(",",0); // Split on each comma, but discard trailing empty strings.
    System.out.println("Limit of -2 produces an array of length " + result1.length);
    System.out.println("Limit of 0 produces an array of length " + result2.length);
  }
}

This outputs the following:

Limit of -2 produces an array of length 9
Limit of 0 produces an array of length 5