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All You Should Know About Substring in Java

25 May 2023
Last updated on: May 25, 2023
Table of Content: What is substring in Java? Use of Substring in Java programming Example of Java substring() method (...
All You Should Know About Substring in Java
Table of Content:

A substring is the part of another string or subset, which is a contiguous sequence of characters within one string. Note that Java is a common language used by web developers, and substring in Java has several applications. This post will give you an insightful understanding of Java substring. Learn more about thread-in-java.

What is Substring in Java?

Want to know about Java substring? Substring in the Java programming language is a common method used for creating smaller strings from bigger ones. Note that strings in Java are immutable, so the original string will be constant while the method brings a new string.

Syntax of Substring in Java?

This method produces the ndexOutofBoundsException only when endIndex is less than the startIndex, endIndex/StartIndex is negative, or endIndex/StartIndex is more than its string's length. Note that in string.substring(int startIndex, int endIndex), the endIndex remains exclusive, although its startindex is inclusive. The string remains an object of its string class. Here's the list of functions:

  1. toLowerCase()changes the case to lowercase
  2. toUpperCase()changes its case to uppercase
  3. Substring() used within the index as the input as well as output
  4. trim() used for removing any unwanted space from the given string

Use of Substring in Java Programming

The substring() function in Java Programming is for extracting only a part of the given string. The function will return the new string that contains a small part of its original string, beginning from its specified index to its end or to a specific end index.

Explanation of the Substring() Method and How it Works

To understand the substring method Java, you need to understand a few things.
All You Should Know About Substring in Java
Suppose you have a string, for instance, "Hello, World!" What if you want to extract the substring "World"? You can do that simply by utilising a substring technique with the help of this:

String str = "Hello, World!";
String substr = str.substring(7, 12);

The Java substring(begIndex, endIndex) process extracts a part of the given string. It then returns the new string that contains the original characters of the string from begIndex (inclusive) to endIndex (exclusive).

String str = "Hello World";
String substr = str.substring(6, 11);
System.out.println(substr); // Output: "World"

Here, the substring() method is on the str string with parameters 6 as well as 11. That means the new substring starts at its index 6 (letter 'W' in "World") & ends at index 11 (last letter is 'd' in "World"). The resulting substring gets assigned to a substrate variable and then printed to its console.

Read More: Find out more about Business Analytics and Data Science courses and other details

Different Parameters Used with the Substring() Method

Java Substring Syntax substring() accepts 2 parameters – start is its index position from which substring begins and is inclusive end is the index position where the substring must end if it is exclusive. As of default, its end value remains equal to the string's length.

Example of Java Substring() Method ( Snippets)

Here's a small example of Java substring() method:

import java.lang.*;
public class StringDemo {
public static void main(String[] args) {
String str = "This is tutorials point";
String substr = "";
// prints the substring after index 8 till index 17
substr = str.substring(8, 17);
System.out.println("substring = " + substr);
// prints the substring after index 0 till index 8
substr = str.substring(0, 8);
System.out.println("substring = " + substr);

Different Substring Operations and Their Applications in Java

 Applications in Java

  Suffix and Prefix extraction

You may consider this if you wish to extract the last name from the given name or digits after its decimal point from the string that contains digits both after & before the point.

  Checking palindrome

It is used for checking whether or not the given string is a palindrome.

 Besides the above-mentioned operations, it is also used for getting substrings of the string.

Explanation of How to Extract a Substring from a Larger String in Java

Java substring may be obtained from the string object via any of the following two variants:

First: Public String substring(int startIndex)

The first method offers a new String object, which includes the string's substring from a specific inclusive startIndex. 

  • Syntax: public String substring(int startIndex)
  • Parameters: startIndex- the starting index (inclusive)
  • Returns: Specified substring 

Second: Public String substring(int startIndex, int endIndex)

This is the second method used for returning the new String object, which may include a substring of the string with indexes between startIndex as well as endIndex. When the second argument is already given, its substring starts with its element at its startIndex to endIndex -1. 

  • Syntax : public String substring(int startIndex, int endIndex)
  • Parameters: startIndex: the starting index, inclusive
  • endIndex: the ending index, exclusive.
  • Return Value: Specified substring.

Overview of Different Substring Operations

Substring is the string manipulation function, which manipulates string data types (such as BLOB, BIT, and CHARACTER). In addition, it extracts characters from one string and creates another. Want to learn about the types of inheritance in Java? Click on the link.

How to Use Java Substrings for String Manipulation

String manipulations are common for any programming language. Java involves a huge amount of built-in functions that fulfil the purpose of string manipulations. One can perform different things in Java, such as getting a string's length, finding a character within the string, and more.

String manipulation is the sequence of characters, which are used in Java. Here, strings are used for creating objects. It isn't a primitive type and is used for creating and storing immutable things. You may take it as the constant as you cannot change it soon after it is created.

You need to use a method (the + operator) to use substrings for string manipulation in the programming language.

String str1= "Hello"; String str2 = "World"; String finalResult = str1+" "+str2; 2.

Changing the string's case, you may change the case of the string using toLowerCase() and toUpperCase() Java built-in functions if and when required.

You can attain details about access-modifiers-in-java.

How to Modify Strings Using Java Substrings?

In Java, you may replace the substring via the replace method. The String class offers an overload version of the method. However, it is imperative to note that you use the replace method (CharSequence target, CharSequence replacement).

Techniques & Methods or Manipulating Strings in Java

Delve into the points to understand the techniques and methods used for manipulating strings in Java:

  • String concatenations: Let's say you have two strings and want them to be concatenated in one. Then, you can use the traditional (the + operator).
  • Changing a given string's case: Changing the case whenever required via toLowerCase() & toUpperCase()
  • Substring inside the string: To check with a certain sequence of characters in the defined string
  • Cleaning a string with an unwanted character: Used for removing the space from the start & end of a given string.
  • String reverse: Used for getting a string from the last index to first

Common Errors and Mistakes when Working with Substrings in Java

Inappropriately Bounded String Copies happen when the data is copied from a particular source to the fixed-length character array

  • Mistakes while copying or concentrating strings
  • Off-by-one blunders are common problems with null-terminated strings, which are similar to unbounded string copies.
  • Failure to null-terminate strings properly: note that a string is null-terminated when the null terminator is present before or at the last element in an array. When the string lacks a terminating null character, a program gets tricked into writing or reading data outside the array's bounds.
  • String truncation occurs when the destination character array isn't large enough to hold a string's content.
  • Errors with functions like strncpy(),strcat(),strtok(),strncat(), or more

Read more about OOPS (Object Oriented Programming) Concept in Java by clicking on the link.

Different Runtime Exceptions that can occur When Using Substrings in Java

Noted below are the runtime exceptions that occur while using substrings in Java

  • The NullPointerException is when any user performs operations on an object considered null or calls for a method on the null object
  • The ArrayIndexOutOfBoundsException occurs when a Java program tries to access a location incorrectly in the non-existent set
  • The InvalidArgumentException is when the invalid parameter is passed to a certain method on the referenced connection of the server

All You Should Know About Substring in Java

Tips for Avoiding Common Errors and Pitfalls

Following these instructions may help avoid common errors:

  • Avoid copying or concentrating strings
  • Ensure that the string does not lack a terminating null character
  • Check that the destination character array is large enough to hold the string's content
  • No errors should be practised with strncpy(),strcat(),strtok(), and strncat()

Best Practices for Working with Substrings in Java

Narrated below are the best practices while working with substrings in Java (learn the  Static Method in Java here):

  • Comparing the two strings by equal()
  • Preferring switch() statement rather than multiple
  • Using string utility class


So, this post has explained everything about substring in Java, starting from substring meaning, definition, methods, different parameters, operations, errors, and best practices.


How do you extract a substring from a larger string in Java?

You may extract the substring from one string via the substring () method. But it is imperative to pass the start as well as end indexes of the substring.

How to write efficient and safe code when working with substrings?

You may use the java substring method (int beginIndex, int endIndex) method of a string class. This method helps return the new string: a string's substring. It starts at the specified beginIndex and then extends to its character at the index endIndex. The substring's length is endIndex-beginIndex.

How to optimise substring operations for performance?

You can optimise and improve java substring operations for performance by selecting the right data type.

What are some common use cases for substrings in java programming?

Java Substring is the string manipulation function, which manipulates the string data types such as BLOB, BIT, and CHARACTER. In addition, it also extracts the characters from the string and creates another. The best use cases for substrings in Java Programming are public class TestSubstring{, public static void main(String args[]){, and more.
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