Java split string

In this article, we will take a look at how to split a string based on a delimiter or separator in java.

Many times you get multiple values from the server or a web service and all the values are separated by a character or a pattern.
Example, details of an employee received from a web server are 123@John@USA where the values separated by @ symbol are the id, name and country of the employee respectively.

Now in order to display or get each of these values separately, you need some mechanism. That is where, split() method becomes useful.

Java string.split() method
split() method belongs to java.lang.String class.
It takes a pattern or a string as argument and breaks the string, on which it is invoked, into parts based on the supplied pattern(or a regular expression).

split() method separates the source string into parts and where every part is created by removing the supplied pattern or regular expression from the source string.

It returns an array whose elements are created by splitting the string on regular expression.

Thus, "123@John@USA".split("@") will return an array whose elements will be 123, John and USA.
Remember that the regular expression on which the string is split is not present in the resulting array. Below are some usage examples of split method.

Also note that the regular expression can be a string of a single character or multiple characters.
split() method types
java.lang.String class contains two overloaded versions of split() method as explained below.

1. split(String pattern)
This method takes a string pattern or regex as an argument and divides the source string based on that pattern.
This method is the same as demonstrated above.

2. split(String pattern, int limit)
This method takes two arguments where the first argument is the string pattern based on which the string will be partitioned and second argument is an integer which determines the number of times, split operation will be applied on the source string.

Limit can have different range of values as follows
A. Positive: If the limit is greater than zero, then the split operation is applied for (limit – 1) times.
Thus, in this case the length of result array will never be greater than the limit.

B. Zero: If the limit is zero, then the split operation will be applied as long as the pattern is present in the source string.
When the limit is zero, then the trailing empty strings will be removed from the result array. This is the same as the single argument split method.

C. Negative: When the limit is less than zero, then the split operation will be applied as long as the pattern is present in the source string as in the previous option but here trailing empty strings will also be present in the resultant array.

Below examples will clarify the meaning of limit values in split(). It is also an example of split a string by dot.
Notice the trailing dot(.) in the source string in the examples.

Method	Result Array Elements	Explanation
String str = "www.codippa.com."; str.split("\\.", 2);	“www”, “codippa.com.”	split operation will be applied for 1 time, therefore only 2 elements will be present in the array. Total split operations = 1
String str = "www.codippa.com."; str.split("\\.", -1);	“www”, “codippa”, “com”, “”	split will be applied till the pattern(.) is present in the string. Notice that the last array element is an empty string. Total split operations = 4
String str = "www.codippa.com."; str.split("\\.", 0);	“www”, “codippa”, “com”	split will be applied till the pattern(.) is present in the string. Notice that the empty string for the last split operation is removed from the array. Total split operations = 4
String str = "www.codippa.com."; str.split("\\.", 3);	“www”, “codippa”, “com.”	Total split operations = 2 Notice the dot(.) in the last array element.
String str = "www.codippa.com."; str.split("\\.");	“www”, “codippa”, “com”	Note that the trailing empty elements are removed

Since the dot is a special character in regular expression, it is required to escape this character, that is why it is preceded with double back slashes(\\).

Java string split() example
Now its time to understand the usage of split method by example programs as follows.

public class SplitDemo {
   public static void main(String[] args) {
      // source string
      String str = "Hi!there!Welcome!to!Java";
      // split the string on a pattern and assign result to array
      String[] arr = str.split("!");
      // iterate over the array
      for (String item : arr) {
         // print the string
         System.out.println(item);
      }
   }
}

Above code when executed prints the below output

Output should be self-explanatory by now.
Java string split by space example
There are two ways to split a string with a space as pattern.
1. Provide a space(” “) as the pattern to the split method.
2. Supply regular expression equivalent to a space which is \\s as the pattern to split method.
Both the approaches are demonstrated below.

public class SplitSpaceDemo {
   public static void main(String[] args) {
      // source string
      String str = "Hi there Welcome";
      // split the string on space
      String[] arr = str.split(" ");
      // iterate over the array
      for (String item : arr) {
         // print the string
         System.out.println(item);
      }
      // split the string on regular expression
      String[] arr = str.split("\\s");
      // iterate over the array
      for (String item : arr) {
         // print the string
         System.out.println(item);
      }
   }
}

Above program produces below output

Similar to the examples above, you can also split a string by comma, dot or any other character in java.
Hope this article must have clarified the concept of split() method in java.lang.String class and its usage.

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