Java String split() method example

The Java String split() returns string array after it splits the string around matches of the method argument regular expression.

1. String split() method

Use String.split() to split a string to string array by tokenizing with delimiter substring or regular expression.

1.1. Method syntax

String split() method is overloaded and comes in two variants.

/**
* @param regex - the delimiting regular expression
* @param limit - the result threshold
* 
* @return - the array of strings
*/
public String[] split(String regex);

public String[] split(String regex, int limit);

1.2. throws PatternSyntaxException

Watch out that split() throws PatternSyntaxException if the regular expression’s syntax is invalid. In given example, "[" is invalid regular expression.

public class StringExample 
{
    public static void main(String[] args) 
    {       
        String[] strArray = "hello world".split("[");
    }
}

Program output.

Exception in thread "main" java.util.regex.PatternSyntaxException: Unclosed character class near index 0
[
^
	at java.util.regex.Pattern.error(Pattern.java:1955)
	at java.util.regex.Pattern.clazz(Pattern.java:2548)
	at java.util.regex.Pattern.sequence(Pattern.java:2063)
	at java.util.regex.Pattern.expr(Pattern.java:1996)
	at java.util.regex.Pattern.compile(Pattern.java:1696)
	at java.util.regex.Pattern.<init>(Pattern.java:1351)
	at java.util.regex.Pattern.compile(Pattern.java:1028)
	at java.lang.String.split(String.java:2367)
	at java.lang.String.split(String.java:2409)
	at com.StringExample.main(StringExample.java:9)

1.3. ‘null’ is not valid method argument

Method does not accept 'null' argument. It will throw NullPointerException in case method argument is null.

Exception in thread "main" java.lang.NullPointerException
	at java.lang.String.split(String.java:2324)
	at com.StringExample.main(StringExample.java:11)

2. Java String split(String regex) example

2.1. Java split string with word or delimiter

Java program to split a string based on some token. In given example, I am splitting string for delimiter hyphen "-".

public class StringExample 
{
    public static void main(String[] args) 
    {
        String str = "how to do-in-java-provides-java-tutorials";
        
        String[] strArray = str.split("-");
        
        System.out.println(Arrays.toString(strArray));
    }
}

Program output.

[how to do, in, java, provides, java, tutorials]

Simialriy,

2.2. Java split string by white space

Java program to split a string by space.

public class StringExample 
{
    public static void main(String[] args) 
    {
        String str = "how to do in java provides java tutorials";
        
        String[] strArray = str.split("\\s");
        
        System.out.println(Arrays.toString(strArray));
    }
}

Program output.

[how, to, do, in, java, provides, java, tutorials]

2.2. Java split string by multiple delimiters

Java program to split a string by multiple delimiters. Use regex OR operator ('|') symbol between multiple delimiters.

public class StringExample 
{
    public static void main(String[] args) 
    {
        String str = "how-to-do-in-java. provides-java-tutorials.";
        
        String[] strArray = str.split("-|\\.");
        
        System.out.println(Arrays.toString(strArray));
    }
}

Program output.

[how, to, do, in, java, provides, java, tutorials]

3. Java String split(String regex, int limit) example

This version of method also splits the string, but maximum number of tokens can not exceed limit argument.

Java program to split a string by space in such as way maximum number of tokens can not exceed '5'.

public class StringExample 
{
    public static void main(String[] args) 
    {
        String str = "how to do in java provides java tutorials";
        
        String[] strArray = str.split("\\s", 5);
        
        System.out.println(strArray.length);	//5
        System.out.println(Arrays.toString(strArray));
    }
}

Program output.

5

[how, to, do, in, java provides java tutorials]

In this example, we learned to split string into array in Java. We saw the examples of how to split a string in java with delimiter.

References:

A Guide to Java String
String Java Doc