Difference between a String and a StringBuffer in Java

In Java, a String is an immutable object that represents a sequence of characters. It means once a String is created, its value cannot be changed, any operation that appears to change the value of a String actually creates a new String object with the new value.

On the other hand, a StringBuffer is a mutable object that also represents a sequence of characters. It means once a StringBuffer is created, its value can be changed, any operation that appears to change the value of a StringBuffer actually modifies the same object.

Here are a few key differences between String and StringBuffer:

• Immutability: As mentioned before, a String is immutable while a StringBuffer is mutable.
• Performance: Because String is immutable, every time you perform a concatenation operation on a String, a new object is created. This can lead to poor performance if you’re concatenating many strings together. StringBuffer is mutable, so it can be modified in place, which is more efficient.
• Thread-safety: StringBuffer is thread-safe, meaning it can be used in a multi-threaded environment without any additional synchronization. On the other hand, String is not thread-safe.
• Methods: StringBuffer has more methods than String, for example, append(), insert(), delete(), reverse(), etc.

In general, if you’re going to perform a lot of string concatenation or modification, you should use a StringBuffer for better performance. If you’re working with a string that will not change, you should use a String

in Java 1.5, a new class StringBuilder is introduced, which is similar to StringBuffer but is not thread-safe. If you don’t need thread-safety use StringBuilder instead, it has the same performance as StringBuffer.