In Java, Substring is a part of a String or can be said subset of the String. There are two variants of the substring() method. This article depicts all of them, as follows :
- public String substring(int startIndex)
- public String substring(int startIndex, int endIndex)
Java Substring
1. String substring()
The substring() method has two variants and returns a new string that is a substring of this string. The substring begins with the character at the specified index and extends to the end of this string. Endindex of the substring starts from 1 and not from 0.
Syntax
public String substring(int begIndex);
Parameters
- begIndex: the begin index, inclusive.
Return Value
- The specified substring.
Example of String substring() Method
Java
// Java code to demonstrate the// working of substring(int begIndex)public class Substr1 { public static void main(String args[]) { // Initializing String String Str = new String("Welcome to neveropen"); // using substring() to extract substring // returns (whiteSpace)neveropen System.out.print("The extracted substring is : "); System.out.println(Str.substring(10)); }} |
The extracted substring is : neveropen
2. String substring(begIndex, endIndex)
This method has two variants and returns a new string that is a substring of this string. The substring begins with the character at the specified index and extends to the end of this string or up to endIndex – 1 if the second argument is given.
Syntax
public String substring(int begIndex, int endIndex);
Parameters
- beginIndex : the begin index, inclusive.
- endIndex : the end index, exclusive.
Return Value
- The specified substring.
Example
Java
// Java code to demonstrate the// working of substring(int begIndex, int endIndex)// Driver Classpublic class Substr2 { // main function public static void main(String args[]) { // Initializing String String Str = new String("Welcome to neveropen"); // using substring() to extract substring // returns geeks System.out.print("The extracted substring is : "); System.out.println(Str.substring(10, 16)); }} |
The extracted substring is : geeks
The complexity of the above method
Time Complexity: O(n), where n is the length of the original string. The substring() method takes constant time O(1) to return the substring.
Space Complexity: O(1), as no extra space is required to perform the substring operation.
Possible Application
The substring extraction finds its use in many applications including prefix and suffix extraction. For example to extract a Lastname from the name or extract only the denomination from a string containing both the amount and currency symbol. The latter one is explained below.
Below is the implementation of the above application
Java
// Java code to demonstrate the// application of substring()// Driver Classpublic class Appli { // main function public static void main(String args[]) { // Initializing String String Str = new String("Rs 1000"); // Printing original string System.out.print("The original string is : "); System.out.println(Str); // using substring() to extract substring // returns 1000 System.out.print("The extracted substring is : "); System.out.println(Str.substring(3)); }} |
The original string is : Rs 1000 The extracted substring is : 1000