Java Interview Guide : 200+ Interview Questions and Answers - Concurrent Collections – CopyOnWriteArrayList

The video tutorial explores advanced collections in Java, focusing on the differences between synchronized and concurrent collections. It explains the limitations of synchronized collections, which use the synchronized keyword, leading to performance issues due to thread waiting. The tutorial introduces concurrent collections, which offer new synchronization approaches like copy on write, compare and swap, and locks. The copy on write approach is detailed, highlighting its efficiency in scenarios with few writes and many reads, such as subject-observer scenarios.

What is a key characteristic of synchronized collections in Java?

• They are only available in Java 8 and above.

• They are faster than concurrent collections.

• They use the synchronized keyword for thread safety.

• They allow multiple threads to execute methods simultaneously.

What is a major drawback of using synchronized collections?

• They are not thread-safe.

• They require a lot of memory.

• They restrict concurrency, affecting performance.

• They are difficult to implement.

Which of the following is NOT a type of concurrent collection approach?

• Synchronized keyword

• Locks

• Compare-and-swap

• Copy-on-write

In the copy-on-write approach, what happens when a new element is added?

• A new array is created with the new element.

• The array is locked permanently.

• The existing array is modified directly.

• The element is added without any locking.

What is an advantage of the copy-on-write approach?

• It uses less memory than other approaches.

• It eliminates the need for locks during reads.

• It is ideal for applications with frequent writes.

• It allows for fast write operations.

In which scenario is the copy-on-write approach particularly useful?

• When there are frequent modifications to the data.

• When memory usage needs to be minimized.

• When there are many read operations and few writes.

• When thread safety is not a concern.

How does the copy-on-write approach handle read operations?

• By synchronizing each read operation.

• By creating a new array for each read.

• By allowing reads without synchronization.

• By locking the array during reads.