In this post, we feature a comprehensive Substring Java Example. We will show how to use Java String substring() API method.
1. Syntax
substring() method can be expressed in two ways:
String substring(int start, int end)String substring(int start)
2. Parameters
start
This parameter is mandatory and it specifies the starting position of the extracted string. Note that first character of string is at index 0 not 1.
end
This parameter is optional and it specifies the end position of the extraction. Note that the index of end position is not included in the extraction.
If end parameter is missing, then the extraction starts from the starting position to the rest of the string.
You can also check the Java String Class Example in the following video:
3. Return value
The return value of substring() method is the extracted string.
4. Substring Java Example
Create a java class named SubstringExample.java with the following code:
SubstringExample.java
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 | public class SubstringExample { public static void main(String args[]) { String str = new String("Javacodegeeks"); System.out.println("Initial string is: " + str); System.out.println("Start position=4 and no end position specified: " + str.substring(4)); System.out.println("Start position=2 and end position=11: " + str.substring(2, 11)); // if start = end, then the extracted string will be empty System.out.println("Start position=3 and end position=3: " + str.substring(3, 3).isEmpty()); // In the following cases we will get // java.lang.StringIndexOutOfBoundException // if (start < 0 or end < 0) System.out.println("Start position=-2 and end position=5: " + str.substring(-2, 5)); // if (start > end) System.out.println("Start position=5 and end position=2: " + str.substring(5, 2)); }} |
Output
Initial string is: Javacodegeeks
Start position=4 and no end position specified: codegeeks
Start position=2 and end position=11: vacodegee
Start position=3 and end position=3: true
Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -2
at java.lang.String.substring(Unknown Source)
at SubstringExample.main(SubstringExample.java:22)
As we see in the output, the substring() method usage is exactly what we described in the previous sections. In the first case, end parameter is omitted, so the extracted string starts from position 2 till the rest of the string.
In the second case, both parameters are defined.
In the third case, we can see that if start position is equal to the end position, then the extracted string is empty.
In the last two cases, we can see that if one of the parameters is less than 0 or start position is greater than end position, then we will have StringIndexOutOfBoundsException.
5. Download the source code
This was an example of Substring Java method.
Download the source code of this example: Substring Java Example
Last updated on Jan. 09, 2020
