Java StringBuffer substring() Method

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The StringBuffer.substring() method in Java is used to retrieve a substring from the StringBuffer 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. substring Method Syntax
3. Examples
   • Retrieving a Substring from a Start Index
   • Retrieving a Substring from a Start Index to an End Index
4. Conclusion

Introduction

The substring() method is a member of the StringBuffer class in Java. It allows you to extract a substring from the StringBuffer and returns it as a new String. This is useful for operations that require working with specific portions of the character sequence without modifying the original StringBuffer.

substring Method Syntax

The syntax for the substring method is as follows:

public synchronized String substring(int start)

Parameters:

• start - the starting index (inclusive) of the substring.

Returns:

• A new String that contains the subsequence of characters from the specified start index to the end of the sequence.

Throws:

• IndexOutOfBoundsException - if start is negative or greater than the length of this sequence.

public synchronized String substring(int start, int end)

Parameters:

• start - the starting index (inclusive) of the substring.
• end - the ending index (exclusive) of the substring.

Returns:

• A new String that contains the subsequence of characters from the specified start index to the specified end index.

Throws:

• IndexOutOfBoundsException - if start or end are negative, if start is greater than end, or if end is greater than the length of this sequence.

Examples

Retrieving a Substring from a Start Index

The substring method can be used to extract a substring from a specified start index to the end of the StringBuffer.

Example

public class StringBufferSubstringExample {
    public static void main(String[] args) {
        // Create a StringBuffer object with initial content
        StringBuffer sb = new StringBuffer("Hello, World!");

        // Retrieve a substring from index 7 to the end
        String subStr = sb.substring(7);

        // Print the substring
        System.out.println("Substring: " + subStr);
    }
}

Output:

Substring: World!

Retrieving a Substring from a Start Index to an End Index

The substring method can also be used to extract a substring from a specified start index to a specified end index.

Example

public class StringBufferSubstringExample {
    public static void main(String[] args) {
        // Create a StringBuffer object with initial content
        StringBuffer sb = new StringBuffer("Hello, World!");

        // Retrieve a substring from index 7 to 12
        String subStr = sb.substring(7, 12);

        // Print the substring
        System.out.println("Substring: " + subStr);
    }
}

Output:

Substring: World

Handling Edge Cases

It is important to handle cases where the specified indices are out of bounds or invalid.

Example

public class StringBufferSubstringExample {
    public static void main(String[] args) {
        // Create a StringBuffer object with initial content
        StringBuffer sb = new StringBuffer("Hello, World!");

        try {
            // Attempt to retrieve a substring with an invalid range
            String subStr = sb.substring(12, 7);
        } catch (IndexOutOfBoundsException e) {
            // Handle the exception
            System.out.println("Error: " + e.getMessage());
        }

        try {
            // Attempt to retrieve a substring with an end index greater than the length
            String subStr = sb.substring(7, 20);
        } catch (IndexOutOfBoundsException e) {
            // Handle the exception
            System.out.println("Error: " + e.getMessage());
        }

        try {
            // Attempt to retrieve a substring with a negative start index
            String subStr = sb.substring(-1, 5);
        } catch (IndexOutOfBoundsException e) {
            // Handle the exception
            System.out.println("Error: " + e.getMessage());
        }
    }
}

Output:

Error: start 12, end 7
Error: end 20
Error: start -1

Conclusion

The StringBuffer.substring() method in Java provides a way to extract a substring from a StringBuffer object and return it as a new String. By understanding how to use this method, you can efficiently work with specific portions of the character sequence without modifying the original StringBuffer. This method is particularly useful for applications that require read-only access to subsequences of the character data.