StringBuilder class

The Java StringBuilder class is used to create and manipulate mutable sequences of characters, just like the StringBuffer class. Both StringBuilder and StringBuffer are designed for the same purpose, but they have different characteristics:

• StringBuilder is not thread-safe, meaning it is not synchronized for multi-threaded operations. This lack of synchronization makes StringBuilder more efficient in single-threaded applications.

Here are some key features and methods of the StringBuilder class:

1. Mutable Character Sequence: A StringBuilder represents a mutable sequence of characters. You can add, modify, or remove characters from the sequence.
2. Not Thread-Safe: Unlike StringBuffer, StringBuilder is not thread-safe. This means that if multiple threads access a StringBuilder concurrently, external synchronization is required to avoid issues.
3. Performance Considerations: StringBuilder is typically preferred in single-threaded scenarios due to its improved performance compared to StringBuffer. However, if you require thread safety, you should use StringBuffer.
4. Constructors:

• StringBuilder(): Creates an empty StringBuilder with a default initial capacity.
• StringBuilder(int capacity): Creates an empty StringBuilder with the specified initial capacity.
• StringBuilder(String str): Creates a StringBuilder initialized with the contents of the specified string.

1. Modifying Operations:

• append(data): Appends various data types to the end of the sequence.
• insert(index, data): Inserts data at the specified position.
• setCharAt(index, ch): Sets the character at the specified index.
• delete(start, end): Deletes characters from the start index (inclusive) to the end index (exclusive).
• deleteCharAt(index): Deletes the character at the specified index.
• replace(start, end, str): Replaces the characters in the specified range with the contents of the provided string.

1. Capacity Management:

• capacity(): Returns the current capacity of the StringBuilder.
• ensureCapacity(minimumCapacity): Ensures that the StringBuilder has at least the specified capacity.
• trimToSize(): Reduces the capacity of the StringBuilder to its current length.

1. String Conversion:

• toString(): Converts the StringBuilder to a String.

1. Other Operations:

• length(): Returns the current length (number of characters) in the StringBuilder.
• charAt(index): Returns the character at the specified index.
• subSequence(start, end): Returns a subsequence from the start index (inclusive) to the end index (exclusive).

Here’s an example of using StringBuilder:

public class StringBuilderExample {
    public static void main(String[] args) {
        StringBuilder sb = new StringBuilder("Hello, ");
        sb.append("World!");
        System.out.println(sb); // Output: Hello, World!

        sb.insert(7, "Java ");
        System.out.println(sb); // Output: Hello, Java World!

        sb.replace(7, 11, "C++");
        System.out.println(sb); // Output: Hello, C++ World!

        sb.delete(7, 11);
        System.out.println(sb); // Output: Hello, World!
    }
}

The StringBuilder is used to build and modify a mutable sequence of characters. You can see how the append, insert, replace, and delete methods are used to manipulate the content.