StringBuffer vs StringBuilder in Java

StringBuffer and StringBuilder are classes in Java used to create and modify mutable strings. Unlike the String class, their content can be changed without creating a new object. They are mainly used when frequent string modifications such as append, insert, or delete operations are required.

• StringBuffer is thread-safe and synchronized, whereas StringBuilder is not synchronized and not thread-safe.
• StringBuffer is slower in performance, whereas StringBuilder is faster and more efficient for single-threaded applications.

StringBuffer Class

StringBuffer is a mutable sequence of characters that is thread-safe. It is designed for multi-threaded environments where multiple threads may modify the same string object.

• StringBuffer is thread-safe because its methods are synchronized.
• Used when multiple threads access the same object.
• Safer for concurrent operations.

Syntax

StringBuffer sb = new StringBuffer("Hello");

class Test {
    public static void main(String[] args) {

        StringBuffer sb1 = new StringBuffer("Hello");
        StringBuffer sb2 = sb1;

        sb1.append(" World");

        if (sb1 == sb2)
            System.out.println("Same");
        else
            System.out.println("Not Same");
    }
}

Same

Explanation:

• sb1 and sb2 refer to the same StringBuffer object
• The append() method modifies the existing object
• No new object is created during modification
• Both references still point to the same memory location

StringBuilder

StringBuilder is a mutable sequence of characters similar to StringBuffer , but it is not thread-safe. It is optimized for single-threaded environments where performance is critical.

• Suitable for single-threaded applications.
• Does not use synchronized methods.
• Faster execution and better performance.

Syntax

StringBuilder sb = new StringBuilder("Hello");

class Test {
    public static void main(String[] args) {

        StringBuilder sb1 = new StringBuilder("Hello");
        StringBuilder sb2 = sb1;

        sb1.append(" World");

        if (sb1 == sb2)
            System.out.println("Same");
        else
            System.out.println("Not Same");
    }
}

Same

Explanation:

• sb1 and sb2 reference the same object
• append() updates the existing StringBuilder instance
• No new object is created after modification
• Faster execution due to lack of synchronization

StringBuilder vs StringBuffer

Below is the key differences table of StringBuffer and StringBuilder.