Java StringBuilder codePointCount() Method

The StringBuilder.codePointCount() method in Java is used to count the number of Unicode code points in a specified range within a StringBuilder object. This guide will cover the method's usage, explain how it works, and provide examples to demonstrate its functionality.

Table of Contents

1. Introduction
2. codePointCount Method Syntax
3. Examples
   • Counting Code Points in a Range
   • Handling IndexOutOfBoundsException
   • Using Code Points for Supplementary Characters
4. Conclusion

Introduction

The StringBuilder.codePointCount() method is a member of the StringBuilder class in Java. It allows you to count the number of Unicode code points within a specified range of the StringBuilder object. This method is particularly useful when dealing with Unicode characters, including supplementary characters that require more than one char value.

codePointCount Method Syntax

The syntax for the codePointCount method is as follows:

public int codePointCount(int beginIndex, int endIndex)

• beginIndex: The index to start counting from (inclusive).
• endIndex: The index to end counting at (exclusive).

Examples

Counting Code Points in a Range

The codePointCount method can be used to count the number of Unicode code points in a specified range within a StringBuilder.

Example

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

        int codePointCount = sb.codePointCount(0, sb.length());

        System.out.println("Number of code points: " + codePointCount);
    }
}

Output:

Number of code points: 13

Handling IndexOutOfBoundsException

Attempting to access an invalid range will result in an IndexOutOfBoundsException. It's important to ensure that the specified range is within the valid bounds of the StringBuilder.

Example

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

        try {
            int invalidCodePointCount = sb.codePointCount(0, 20); // This will throw an exception
            System.out.println("Number of code points: " + invalidCodePointCount);
        } catch (IndexOutOfBoundsException e) {
            System.out.println("Error: " + e.getMessage());
        }
    }
}

Output:

Error: begin 0, end 20, length 13

Using Code Points for Supplementary Characters

For supplementary characters (characters outside the Basic Multilingual Plane, BMP), which are represented by a pair of char values (a surrogate pair), the codePointCount method can be used to get the correct number of code points.

Example

public class StringBuilderCodePointCountExample {
    public static void main(String[] args) {
        StringBuilder sb = new StringBuilder("Hello, World! \uD83D\uDE00"); // Unicode for 😀 (grinning face)

        int codePointCount = sb.codePointCount(0, sb.length());

        System.out.println("Number of code points including emoji: " + codePointCount);
    }
}

Output:

Number of code points including emoji: 14

In this example, the string "Hello, World! 😀" has 14 code points because the emoji counts as a single supplementary character.

Conclusion

The StringBuilder.codePointCount() method in Java is used for counting the number of Unicode code points within a specified range of a StringBuilder object. By understanding how to use this method, you can efficiently handle and analyze sequences of Unicode characters, including supplementary characters. Whether you need to count code points in a range, handle potential exceptions, or work with characters beyond the BMP, the codePointCount method provides a reliable solution for these tasks.