Find Index of a Particular String Example in Java

Introduction

Find Index Of A Particular String is a classic Java console program that demonstrates the concept with complete source code and sample output. Strings are immutable objects in Java; the examples show comparison, searching and transformation.

This tutorial walks through the program line by line, explains how the logic works, and highlights best practices you can apply in your own code.

Definition

This method indexOf() is an inbuilt method of strings which is used to find the index of a particular character or string.

Syntax

int indexOf(String str)

Find Index Of A Particular String Example Program

import java.util.Scanner;

class FindIndexOfString { 
	public static void main(String args[]) { 
		Scanner in=new Scanner(System.in);
		String str1="";
		String str2 = "Hard work pays"; 
		System.out.println(str2); 
		System.out.print("Enter the character for which the index is to be found: ");
		str1=in.next();
		System.out.println("index Of the character is " +str2.indexOf(str1));  
	}
}

Sample Output

Hard work pays
Enter the character for which the index is to be found: pays
index Of the character is 10

When to use

Use string manipulation when cleaning user input, parsing text files or formatting messages.

How it works

1. Execution begins in the main method — the JVM calls this method when you run the class.

2. import java.util.Scanner; imports a class used later in the program.

3. A Scanner reads typed input from the keyboard (System.in).

4. String str1=""; updates a variable used in the calculation or output.

5. String str2 = "Hard work pays"; updates a variable used in the calculation or output.

6. A println / print call writes text to the console — part of the sample output below.

7. A println / print call writes text to the console — part of the sample output below.

8. A println / print call writes text to the console — part of the sample output below.

Best Practices

• Use meaningful variable and class names that describe their purpose.
• Compile and run the program locally — modify values to see how output changes.
• Read compiler errors carefully; they usually point to the exact line to fix.

Common Mistakes

• Copying code without understanding each line — practice by changing one statement at a time.
• Mismatching the public class name and the .java filename.
• Forgetting semicolons at the end of statements.