StringBuffer Class in Java

StringBuffer class in Java represents a sequence of characters that can be modified, which means we can change the content of the StringBuffer without creating a new object every time. It represents a mutable sequence of characters.

• Unlike String, we can modify the content of the StringBuffer without creating a new object.
• All methods of StringBuffer are synchronized, making it safe to use in multithreaded environments.
• Ideal for scenarios with frequent modifications like append, insert, delete or replace operations.

Example: Here is an example of using StringBuffer to concatenate strings.

Hello world

Interface Hierarchy Implemented by StringBuffer

The diagram shows the interfaces implemented by StringBuffer and illustrates its relationship with Appendable, CharSequence, and Serializable in Java.

Constructors of StringBuffer Class

• StringBuffer(): It reserves room for 16 characters without reallocation
• StringBuffer(int size): It accepts an integer argument that explicitly sets the size of the buffer.
• StringBuffer(String str): It accepts a string argument that sets the initial contents of the StringBuffer object and reserves room for 16 more characters without reallocation.

Example:

Default Constructor: Hello
With Capacity 50: Java Programming
With String: Welcome to Java

Implementation of Java StringBuffer Method

1. append() Method

append() method concatenates the given argument with this string.

Hello Java

2. insert() Method

insert() method inserts the given string with this string at the given position. 

HJavaello 

3. replace() Method

replace() method replaces the given string from the specified beginIndex and endIndex-1.

HJavalo

4. delete() Method

delete() method is used to delete the string from the specified beginIndex to endIndex-1.

Hlo

5. reverse() Method

reverse() method of the StringBuffer class reverses the current string. 

olleH

6. capacity() Method

capacity() method of the StringBuffer class returns the current capacity of the buffer. The default capacity of the buffer is 16. If the number of characters increases from its current capacity, it increases the capacity by (oldcapacity*2)+2.

For example, if the current capacity is 16, it will be (16*2)+2=34.

16
16
34

7. length()

This method return the number of character in given string.

Length of string GeeksforGeeks=13

Advantages:

• Mutable: Its content can be modified after creation while String remains immutable.
• Better for Repeated Updates: Frequent concatenations perform efficiently because no new objects are created for each change.
• Thread-Safe: All methods are synchronized, making it safe in multithreaded environments.

Limitations:

• Performance Overhead: Synchronization makes operations slower compared to non-synchronized alternatives.
• Not Ideal for Single-Threaded Applications: When thread safety is unnecessary, it adds extra processing cost.
• Lower Performance Than StringBuilder: StringBuilder is preferred in non-threaded scenarios because it is faster.

StringBuffer all Methods