What are the differences between String, StringBuffer, and StringBuilder in Java?

Differences between String, StringBuffer, and StringBuilder in Java

In Java, String, StringBuffer, and StringBuilder are all used to represent and manipulate sequences of characters, but they have some key differences in terms of their functionality, performance, and thread-safety.

String

The String class in Java represents an immutable sequence of characters. This means that once a String object is created, its value cannot be changed. Any operation that appears to modify a String object actually creates a new String object with the desired changes.

String s1 = "Hello";
s1 = s1 + ", world!"; // Creates a new String object "Hello, world!"

String objects are thread-safe, which means they can be safely accessed by multiple threads without the need for explicit synchronization.

StringBuffer

The StringBuffer class in Java represents a mutable sequence of characters. Unlike String, StringBuffer objects can be modified after they are created. StringBuffer provides synchronized methods for thread-safe operations, making it suitable for use in multi-threaded environments.

StringBuffer sb = new StringBuffer("Hello");
sb.append(", world!"); // Modifies the existing StringBuffer object

StringBuffer is thread-safe, which means its methods are synchronized, ensuring that only one thread can access the object at a time.

StringBuilder

The StringBuilder class in Java is similar to StringBuffer, but it is not thread-safe. StringBuilder provides the same methods as StringBuffer for modifying the sequence of characters, but it does not have the overhead of synchronization.

StringBuilder sb = new StringBuilder("Hello");
sb.append(", world!"); // Modifies the existing StringBuilder object

StringBuilder is not thread-safe, which means its methods are not synchronized. This makes StringBuilder more efficient than StringBuffer in single-threaded environments, as it avoids the overhead of synchronization.

In summary, the main differences between String, StringBuffer, and StringBuilder are:

1. Mutability: String is immutable, while StringBuffer and StringBuilder are mutable.
2. Thread-safety: StringBuffer is thread-safe, while StringBuilder is not.
3. Performance: StringBuilder is generally faster than StringBuffer in single-threaded environments due to the absence of synchronization overhead.

The choice between String, StringBuffer, and StringBuilder depends on the specific requirements of your application, such as the need for thread-safety, the frequency of string manipulations, and the performance requirements.