StringBuffer

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StringBuffer class in Java

StringBuffer is a class in Java that represents a mutable sequence of characters. It provides an alternative to the immutable String class, allowing you to modify the contents of a string without creating a new object every time.

Java Program Demonstrating  Basic StringBuffer Methods

public class StringBufferExample {
    public static void main(String[] args) {
        // Create a StringBuffer object
        StringBuffer sb = new StringBuffer("adib mahfuj");

        // Append a string to the end
        sb.append(" is a student");
        System.out.println("After append: " + sb);

        // Insert a string at a specified position
        sb.insert(5, "k ");
        System.out.println("After insert: " + sb);

        // Reverse the contents of the StringBuffer
        sb.reverse();
        System.out.println("After reverse: " + sb);
        sb.reverse(); // Reverse it back to original

        // Replace a portion of the string with another string
        sb.replace(5, 7, "A");
        System.out.println("After replace: " + sb);

        // Delete a portion of the string
        sb.delete(5, 6);
        System.out.println("After delete: " + sb);

        // Delete a character at a specified position
        sb.deleteCharAt(5);
        System.out.println("After deleteCharAt: " + sb);

        // Get the current length of the buffer
        int length = sb.length();
        System.out.println("Length: " + length);

        // Get the capacity of the buffer
        int capacity = sb.capacity();
        System.out.println("Capacity: " + capacity);

        // Ensure the capacity is at least a specified minimum
        sb.ensureCapacity(50);
        System.out.println("Capacity after ensureCapacity: " + sb.capacity());

        // Set the length of the buffer
        sb.setLength(8);
        System.out.println("After setLength: " + sb);

        // Get a character at a specified index
        char charAt = sb.charAt(2);
        System.out.println("Character at index 2: " + charAt);

        // Set a character at a specified index
        sb.setCharAt(2, 'D');
        System.out.println("After setCharAt: " + sb);

        // Get a substring from the buffer
        String substring = sb.substring(2, 6);
        System.out.println("Substring (2, 6): " + substring);

        // Convert the buffer to a string
        String resultString = sb.toString();
        System.out.println("ToString: " + resultString);
    }
}

Explanation

  • Creating a StringBuffer Object:
  • StringBuffer sb = new StringBuffer("adib mahfuj");
  • This line creates a StringBuffer object named sb initialized with the string "adib mahfuj". StringBuffer is used to create strings that can be modified.

  • Appending a String:
  • sb.append(" is a student");
  • The append method adds the string " is a student" to the end of the current string. 

  • Inserting a String:
  • sb.insert(5, "k ");
  • The insert method inserts the string "k " at position 5. Positions are zero-based, so position 5 is after "adib ".

  • Reversing the StringBuffer:
  • sb.reverse();  sb.reverse();
  • The reverse method reverses the characters in the StringBuffer. The second reverse call returns it to the original order.

  • Replacing a Portion of the String:
  • sb.replace(5, 7, "A");
  • The replace method replaces the characters from position 5 to 7 with "A".

  • Deleting a Portion of the String:
  • sb.delete(5, 6);
  • The delete method removes the characters from positions 5 to 6.

  • Deleting a Character:
  • sb.deleteCharAt(5);
  • The deleteCharAt method removes the character at position 5.

  • Getting the Length:
  • int length = sb.length();
  • The length method returns the number of characters in the StringBuffer.

  • Getting the Capacity:
  • int capacity = sb.capacity();
  • The capacity method returns the current capacity of the StringBuffer, which is the amount of storage available for new characters without resizing.
  • Ensuring Minimum Capacity:
  • sb.ensureCapacity(50);
  • The ensureCapacity method ensures that the StringBuffer has at least the specified capacity (50 in this case).
  • Setting the Length:
  • sb.setLength(8);
  • The setLength method sets the length of the StringBuffer. If the new length is shorter, the buffer is truncated.
  • Getting a Character:
  • char charAt = sb.charAt(2);
  • The charAt method returns the character at the specified position (index 2).
  • Setting a Character:
  • sb.setCharAt(2, 'D');
  • The setCharAt method sets the character at the specified position (index 2) to 'D'.
  • Getting a Substring:
  • String substring = sb.substring(2, 6);
  • The substring method returns a new string that starts from index 2 and ends at index 6 (excluding 6).
  • Converting to String:
  • String resultString = sb.toString();
  • The toString method converts the StringBuffer to a String.








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