What is atomicity?

Atomicity is one of the key properties of transactions in databases, meaning that a transaction is executed as a single unit: either all operations within the transaction successfully complete, or none of them are applied.

If an error occurs during the execution of a transaction, all changes are rolled back, and the database is returned to its state before the transaction began. This guarantees data integrity and prevents partial application of changes.

Example: when transferring money between bank accounts, a transaction must ensure that the debit from one account and the credit to another happen together. If one operation fails, both are canceled to prevent balance discrepancies.

In Java, atomicity is often ensured through transaction management tools (e.g., via JDBC or frameworks like Spring), as well as using classes from the java.util.concurrent.atomic package, which provide atomic operations on variables in a multithreaded environment.