Which of this method of class String is used to extract a substring from a String object

Java String substring[] method returns the substring of this string. This method always returns a new string and the original string remains unchanged because String is immutable in Java.

Java String substring[] Methods

1. substring[int beginIndex]: This method 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.
2. substring[int beginIndex, int endIndex]: The substring begins at the specified beginIndex and extends to the character at index endIndex - 1. Thus the length of the substring is [endIndex - beginIndex].

String substring[] Method Important Points

1. Both the string substring methods can throw IndexOutOfBoundsException if any of the below conditions met.
   • if the beginIndex is negative
   • endIndex is larger than the length of this String object
   • beginIndex is larger than endIndex
2. beginIndex is inclusive and endIndex is exclusive in both substring methods.

Java String substring[] Example

Here is a simple program for the substring in java.

package com.journaldev.util;

public class StringSubstringExample {

	public static void main[String[] args] {
		String str = "www.journaldev.com";
		System.out.println["Last 4 char String: " + str.substring[str.length[] - 4]];
		System.out.println["First 4 char String: " + str.substring[0, 4]];
		System.out.println["website name: " + str.substring[4, 14]];
	}
}

Output of the above substring example program is:

Last 4 char String: .com
First 4 char String: www.
website name: journaldev

Checking Palindrome using substring[] Method

We can use the substring[] method to check if a String is a palindrome or not.

package com.journaldev.util;

public class StringPalindromeTest {
	public static void main[String[] args] {
		System.out.println[checkPalindrome["abcba"]];
		System.out.println[checkPalindrome["XYyx"]];
		System.out.println[checkPalindrome["871232178"]];
		System.out.println[checkPalindrome["CCCCC"]];
	}

	private static boolean checkPalindrome[String str] {
		if [str == null]
			return false;
		if [str.length[]