@@ -80,6 +80,68 @@ The benchmark was executed across three cases varying the number of threads and
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### ✅ Conclusion
## 🚀 IV. Optional Challenge: `removeGroup` (Part 2)
> For data structures that are read more frequently than they are written, the **Read/Write Lock (`RWLockList`)** is the mandatory choice for achieving high throughput and maximum parallelism without sacrificing thread safety.
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### A. The Requirement
The optional second part of the question required the implementation of a `removeGroup(Collection<Integer> items)` method. The prompt specifically asked for this to be implemented **only in `RWLockList`** while maintaining *"general isolation"* (العزل العام) against single `remove` operations.
### B. Solution
* The `removeGroup` method was added **directly to `RWLockList.java`** without adding it to the `SortList` abstract class. This maintains the separation requested by the assignment.
* The implementation fulfills the requirement by using the **global `writeLock()`**.
### C. Interpretation
This implementation is correct and meets the assignment's criteria:
***Atomicity**: By holding the single `writeLock()` for the entire duration of the loop, the `removeGroup` method is atomic. No other thread can `add`, `remove`, `contain`, or `removeGroup` while a group removal is in progress.
***Maintains "General Isolation"**: This implementation correctly maintains the *"general isolation"* (العزل العام) required by the prompt. It ensures that this new method is thread-safe with all other existing methods (`add`, `remove`, `contain`) which also rely on the same global lock.
### D. Unit Test Verification
To confirm the logical correctness of `removeGroup`, the following single-threaded test was added to `SyncListTest.java`. This test verifies the return value, final list length, and success/failure counters.
assertEquals("Should have removed 2 items",2,removedCount);
assertEquals("List length should be 3",3L,list.length);
assertTrue("List should still be sorted",list.checkSorted());
assertFalse("Item 5 should be removed",list.contain(5));
assertFalse("Item 15 should be removed",list.contain(15));
assertTrue("Item 10 should still be present",list.contain(10));
assertEquals("Remove success count should be 2",2,list.removeSuccess.get());
assertEquals("Remove failure count should be 2",2,list.removeFailure.get());
System.out.println("\nremoveGroup test passed.");
}
```
## V. Overall Project Conclusion
This project successfully demonstrated the critical performance differences between common Java concurrency models.
The benchmark results from Part 1 definitively prove that `ReentrantReadWriteLock` is the superior choice for read-heavy workloads, offering up to a **7× performance increase** by enabling parallel reads. The correctness checks (`checkSorted()`, consistent counts) simultaneously proved that all three locking strategies were implemented correctly and successfully prevented any race conditions.
The optional challenge from Part 2 extended this by implementing an atomic `removeGroup` method. By protecting this new write-based method with the same global `writeLock()`, we ensured that all write operations (single `add`, single `remove`, and group `remove`) remain fully thread-safe and maintain *"general isolation"* against each other.
In summary, the project fulfills all assignment requirements by benchmarking performance, verifying data integrity under concurrent stress, and successfully implementing the optional extension, confirming the `RWLockList` as the most robust and high-performance solution for this problem.
