Java StringBuilder setLength() Method

The StringBuilder.setLength() method in Java is used to set the length of the StringBuilder object. 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.setLength() can be used effectively.

Table of Contents

1. Introduction
2. setLength Method Syntax
3. Examples
   • Increasing the Length of a StringBuilder
   • Decreasing the Length of a StringBuilder
4. Real-World Use Case
   • Example: Truncating a String to a Specific Length
5. Conclusion

Introduction

The StringBuilder.setLength() method is a member of the StringBuilder class in Java. It allows you to set the length of the StringBuilder object. If the new length is greater than the current length, null characters (\u0000) are appended. If the new length is less than the current length, the StringBuilder is truncated.

setLength Method Syntax

The syntax for the setLength method is as follows:

public void setLength(int newLength)

• Parameters:
  • newLength: The new length of the StringBuilder.
• Returns: This method does not return a value.

Examples

Increasing the Length of a StringBuilder

If the new length is greater than the current length, null characters (\u0000) are appended to the StringBuilder.

Example

public class IncreaseLengthExample {
    public static void main(String[] args) {
        StringBuilder sb = new StringBuilder("Hello");

        // Increasing the length of the StringBuilder to 10
        sb.setLength(10);

        // Printing the modified StringBuilder
        System.out.println("StringBuilder: '" + sb.toString() + "'");
        System.out.println("Length: " + sb.length());
    }
}

Output:

StringBuilder: 'Hello�����'
Length: 10

Decreasing the Length of a StringBuilder

If the new length is less than the current length, the StringBuilder is truncated.

Example

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

        // Decreasing the length of the StringBuilder to 5
        sb.setLength(5);

        // Printing the modified StringBuilder
        System.out.println("StringBuilder: '" + sb.toString() + "'");
        System.out.println("Length: " + sb.length());
    }
}

Output:

StringBuilder: 'Hello'
Length: 5

Real-World Use Case

Example: Truncating a String to a Specific Length

A common real-world use case for StringBuilder.setLength() is truncating a string to a specific length, such as when displaying a preview of a longer text.

Example

public class TruncateStringExample {
    public static void main(String[] args) {
        StringBuilder text = new StringBuilder("This is a long text that needs to be truncated.");

        // Truncating the text to 20 characters
        int maxLength = 20;
        if (text.length() > maxLength) {
            text.setLength(maxLength);
            text.append("...");
        }

        // Printing the truncated text
        System.out.println("Truncated text: " + text.toString());
    }
}

Output:

Truncated text: This is a long text...

In this example, StringBuilder.setLength() is used to truncate a long text to a specific length and append an ellipsis, demonstrating how it can be useful for creating previews or summaries.

Conclusion

The StringBuilder.setLength() method in Java provides a way to set the length of the StringBuilder object. By understanding how to use this method, you can efficiently manipulate the length of strings in your Java applications. The method allows you to increase or decrease the length of the StringBuilder, making it a versatile tool for various string manipulation tasks.