Replace Character in a String Example in Java

Introduction

Replace Character In A 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.

Replace Character In A String Example Program

public class ReplaceCharacterInString{
   public static void main(String args[]){
      String str ="This is a Java Dutorial";
      System.out.println("The input string is:  "+str );
	  System.out.println("After replacement, the string is: ");
      System.out.println(str.replace('D', 'T'));
   }
}

Sample Output

The input string is:  This is a Java Dutorial
After replacement, the string is:
This is a Java Tutorial

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 ="This is a Java Dutorial"; 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. Compare your console output with the sample output for Replace Character In A String to confirm the program behaves correctly.

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.