Java StringBuilder replace() Method

The StringBuilder.replace() method in Java is used to replace a sequence of characters in a StringBuilder object with another string. This guide will cover the method's usage, explain how it works, and provide examples to demonstrate its functionality. We will also cover a real-world use case to show how StringBuilder.replace() can be used effectively.

Table of Contents

1. Introduction
2. replace Method Syntax
3. Examples
   • Replacing a Substring in a StringBuilder
   • Replacing a Substring with an Empty String
4. Real-World Use Case
   • Example: Censoring Sensitive Information
5. Conclusion

Introduction

The StringBuilder.replace() method is a member of the StringBuilder class in Java. It allows you to replace a sequence of characters between specified start and end indices with another string. This method is useful for modifying portions of a string within a StringBuilder object.

replace Method Syntax

The syntax for the replace method is as follows:

public StringBuilder replace(int start, int end, String str)

• Parameters:
  • start: The beginning index, inclusive.
  • end: The ending index, exclusive.
  • str: The string that will replace the specified sequence of characters.
• Returns: A reference to the same StringBuilder object, with the specified sequence of characters replaced by the new string.

Examples

Replacing a Substring in a StringBuilder

The replace method can be used to replace a specific substring within a StringBuilder object.

Example

public class ReplaceExample {
    public static void main(String[] args) {
        StringBuilder sb = new StringBuilder("Hello, world!");

        // Replacing the substring "world" with "Java"
        sb.replace(7, 12, "Java");

        // Printing the modified StringBuilder
        System.out.println(sb.toString());
    }
}

Output:

Hello, Java!

Replacing a Substring with an Empty String

You can replace a substring with an empty string, effectively removing that substring from the StringBuilder.

Example

public class RemoveSubstringExample {
    public static void main(String[] args) {
        StringBuilder sb = new StringBuilder("Hello, world!");

        // Removing the substring "world"
        sb.replace(7, 12, "");

        // Printing the modified StringBuilder
        System.out.println(sb.toString());
    }
}

Output:

Hello, !

Real-World Use Case

Example: Censoring Sensitive Information

A common real-world use case for StringBuilder.replace() is censoring sensitive information in a text, such as replacing certain words with asterisks.

Example

public class CensorSensitiveInfo {
    public static void main(String[] args) {
        StringBuilder text = new StringBuilder("This is a confidential document. Do not share this document.");

        // Censoring the word "confidential"
        int start = text.indexOf("confidential");
        int end = start + "confidential".length();
        text.replace(start, end, "***********");

        // Printing the censored text
        System.out.println(text.toString());
    }
}

Output:

This is a *********** document. Do not share this document.

In this example, StringBuilder.replace() is used to censor the word "confidential" by replacing it with asterisks, demonstrating how it can be useful for modifying text to hide sensitive information.

Conclusion

The StringBuilder.replace() method in Java provides a way to replace a sequence of characters within a StringBuilder object with another string. By understanding how to use this method, you can efficiently modify portions of strings in your Java applications. The method allows you to perform various string replacement operations, making it a versatile tool for string manipulation in various scenarios.