Split a string using String.split()Tag(s): String/Number

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http://www.rgagnon.com/javadetails/java-0438.html


The String class has a split() (since 1.4) method that will return a String array.

public class StringSplit {  public static void main(String args[]) throws Exception{    String testString = "Real-How-To";    System.out.println      (java.util.Arrays.toString(testString.split("-")));    // output : [Real, How, To]  }}

split() is based on regex expression, a special attention is neededwith some characters which have a special meaning in a regex expression.

For example :

public class StringSplit {  public static void main(String args[]) throws Exception{    String testString = "Real.How.To";    // bad    System.out.println       (java.util.Arrays.toString(testString.split(".")));    // output : []    // good    System.out.println       (java.util.Arrays.toString(testString.split("\\.")));    // output : [Real, How, To]  }}
And
public class StringSplit {  public static void main(String args[]) throws Exception{    String testString = "Real|How|To";    // bad    System.out.println       (java.util.Arrays.toString(testString.split("|")));    // output : [, R, e, a, l, |, H, o, w, |, T, o]    // good    System.out.println       (java.util.Arrays.toString(testString.split("\\|")));    // output : [Real, How, To]  }}
The special character needs to be escaped with a "\" but since "\"is also a special character in Java, you need to escape it again with another "\" !
Consider this example
public class StringSplit {  public static void main(String args[]) throws Exception{    String testString = "Real|How|To|||";    System.out.println       (java.util.Arrays.toString(testString.split("\\|")));    // output : [Real, How, To]  }}
The result does not include the empty strings between the "|" separator.To keep the empty strings :
public class StringSplit {  public static void main(String args[]) throws Exception{    String testString = "Real|How|To|||";    System.out.println       (java.util.Arrays.toString(testString.split("\\|", -1)));    // output : [Real, How, To, , , ]  }}
See split(String.int).
String.split() is only available since JDK 1.4.

With previous version, java.util.StringTokeniser can be used.

See this HowTo


Some notes from A. Gonzales about String.split()

Special cases using String.split():

public class StringSplit {  public static void main(String args[]) throws Exception{    System.out.println       (java.util.Arrays.toString("  s".split(" ")));    // output : [, , s]    System.out.println       (java.util.Arrays.toString("".split("")));    // output : []    System.out.println       (java.util.Arrays.toString("  ".split(" ")));    // output : []    System.out.println       (java.util.Arrays.toString("      ".split(" ")));    // output : []    System.out.println       (java.util.Arrays.toString(" s ".split(" ")));    // output : [, s]  }}

It's important to note that an invocation like:
param = req.getParam(...);String[] words = param.split(" ");String firstWord = words[0];
will generate a NullPointerException if param.equals(" ").
Using split() with a space can be a problem. Consider the following :
public class StringSplit {  public static void main(String args[]) throws Exception{    String testString = "Real  How To";  // extra space    System.out.println       (java.util.Arrays.toString(testString.split(" ")));    // output : [Real, , How, To]  }}
We have an extra element.The fix is to specify a regular expression to match one or more spaces.
public class StringSplit {  public static void main(String args[]) throws Exception{    String testString = "Real  How To";    System.out.println       (java.util.Arrays.toString(testString.split("\\s+")));    // output : [Real, How, To]  }}

Since String.split() is based on regular expression, you can make somecomplex operations with a simple call!
  String testString = "{RealHowto}{java-0438.html}{usage of String.split()}";  System.out.println     (java.util.Arrays.toString(testString.split("[{}]")));  // output : [, RealHowto, , java-0438.html, , usage of String.split()]  // note : extra empty elements :-(

To split a long string into into fixed-length parts. In this example, we split in groups of 3 characters :
  String testString = "012345678901234567890";  System.out.println     (java.util.Arrays.toString(testString.split("(?<=\\G.{3})")));  // output : [012, 345, 678, 901, 234, 567, 890]

To split but keep the separator :
   String testString = "RealHowto!java-0438.html!usage of String.split()!";   System.out.println      (java.util.Arrays.toString(testString.split("(?<=[!])")));   // output : [RealHowto!, java-0438.html!, usage of String.split()!]

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