Explanations “Top Java Quiz Questions”

What will be the output of the code?

❌ A. Counter value: 20000
✅ B. Counter value: Less than 20000
❌ C. Counter value: More than 20000
❌ D. Compilation error
❌ E. Runtime error
❌ F. None of the above

Explanation:
This code snippet demonstrates a scenario where two threads (t1 and t2) increment a shared static variable counter. Each thread iterates 10000 times and increments the counter.

Due to the concurrent nature of multithreading, the increment operation (counter++) is not atomic. It consists of reading the current value of counter, adding 1 to it, and then writing the new value back. This introduces a race condition.

It's possible that while one thread is performing the read-modify-write operation, the other thread may perform a similar operation concurrently, causing the updates to overlap and potentially leading to lost updates.

The correct answer is option B) Counter value: Less than 20000. The exact output value can vary due to the race condition. The threads might interfere with each other's updates, causing some increments to be lost. Therefore, the output value will likely be less than 20000.

In a multithreaded scenario like this, proper synchronization mechanisms (e.g., synchronized keyword or AtomicInteger) should be used to ensure the correct behavior of shared variables.

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1.4K viewsedited  Aug 18, 2023 at 16:38

What will be the output of the code?

❌ A. Counter value: 20000
✅ B. Counter value: Less than 20000
❌ C. Counter value: More than 20000
❌ D. Compilation error
❌ E. Runtime error
❌ F. None of the above

Explanation:
This code snippet demonstrates a scenario where two threads (t1 and t2) increment a shared static variable counter. Each thread iterates 10000 times and increments the counter.

Due to the concurrent nature of multithreading, the increment operation (counter++) is not atomic. It consists of reading the current value of counter, adding 1 to it, and then writing the new value back. This introduces a race condition.

It's possible that while one thread is performing the read-modify-write operation, the other thread may perform a similar operation concurrently, causing the updates to overlap and potentially leading to lost updates.

The correct answer is option B) Counter value: Less than 20000. The exact output value can vary due to the race condition. The threads might interfere with each other's updates, causing some increments to be lost. Therefore, the output value will likely be less than 20000.

In a multithreaded scenario like this, proper synchronization mechanisms (e.g., synchronized keyword or AtomicInteger) should be used to ensure the correct behavior of shared variables.

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