Find Index of a Particular Character Example in Java

Introduction

Find Index Of A Particular Character 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

public int indexOf(int ch )

Find Index Of A Particular Character Example Program

public class FindIndexOfCharacter {
	public static void main(String args[]) {
		String Str = new String("abcdefghijklmnopqrstuvwxyz");
		System.out.print("Index of o is :" );
		System.out.println(Str.indexOf( 'o' ));
		System.out.print("Index of f is :" );
		System.out.println(Str.indexOf( 'f'));
		System.out.print("Index of w is :" );
		System.out.println( Str.indexOf('w'));
		System.out.print("Index of g is :" );
		System.out.println( Str.indexOf('g'));
	}
}

Sample Output

Index of o is :14
Index of f is :5
Index of w is :22
Index of g is :6

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. String Str = new String("abcdefghijklmnopqrstuvwxyz"); updates a variable used in the calculation or output.

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

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

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

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.