| Immutability |
Immutable: Once a String object is created, its content cannot be altered. |
Mutable: The content can be changed after the object is created. |
| Performance |
Concatenating String objects using the + operator can be inefficient in loops because a new String object is created with every concatenation. |
Offers better performance for multiple modifications, like append or delete, since it doesn’t create a new instance with every modification. |
| Methods |
Provides a wide range of functionality but does not support modification operations like append, insert, or delete. |
Supports methods for string manipulation like append(), insert(), delete(), and reverse(). |
| Thread Safety |
Thread-safe because of its immutability. |
Thread-safe because all the crucial methods (append, insert, delete, etc.) are synchronized. |
| Memory Overhead |
Every operation creating a new String can lead to memory overhead if done frequently, as many temporary objects are generated. |
Has a lower memory overhead compared to String for operations, as it avoids creating many temporary objects. |
| Use-case |
Best for strings that won’t be modified. |
Best for strings requiring frequent modifications, especially in a multi-threaded environment. |
| Storage |
Stored in the String pool. |
Stored in the heap (outside the String pool). |