2025 Jan CD short q's

3 processes share 4 resource units, max 2 each — show deadlock cannot occur.

Worst case: all 3 hold 1 unit and wait for a 2nd. Only 3 of 4 units used, 1 spare. Circular wait can't happen because the spare can be given to a waiting process.

What are the four key characteristics of fair locks? Explain each one.

FIFO ordering, no barging, lower throughput, created with new ReentrantLock(true).

What are the benefits of immutable streams?

A stream never modifies its source, so it's inherently thread safe to read from.

What is object serialization, and how do you implement it?

Serialization turns an object's state into bytes. Implement it via Serializable, or Externalizable, which needs writeExternal() and readExternal().

Explain what is meant by encapsulated classes.

Encapsulation bundles a class's data with the methods that operate on it, while hiding the internal state from the outside.

What is a non-blocking, lock-free data structure?

A lock-free structure stays thread safe without locks, usually using compare-and-swap. Some thread always makes progress, so there's no deadlock, but threads may retry under contention.