| Immutability |
Immutable: Once a String object is created, its content cannot be changed. |
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 when making multiple modifications, like append or delete, as it doesn’t create a new instance every time. |
| Methods |
Has methods to provide a wide range of functionality, but does not support modification operations like append, insert, or delete. |
Provides methods for string manipulation like append(), insert(), delete(), and reverse(). |
| Thread Safety |
Thread-safe due to its immutability. |
Not thread-safe. If needed in a multi-threaded environment, one must ensure proper synchronization. |
| Memory Overhead |
Every operation creating a new String may lead to an overhead if done frequently, as it leads to the creation of many temporary objects. |
Has a lower memory overhead for string operations because it reuses the same object for modifications, thus avoiding the creation of multiple temporary objects. |
| Use-case |
Best for strings that won’t change in terms of content. |
Best for strings that need frequent modifications, like in loops or when concatenating/appending values repeatedly. |
| Storage |
Stored in the String pool. |
Stored in the heap (outside the String pool). |