1Z0-819 Exception Handling & Concurrency 4

Question 1

What is a deadlock in concurrent programming?

Accepted Answer

Two or more threads each waiting for a lock held by the other

Answer

Deadlock is a circular wait condition where thread A holds lock X and wants Y, while thread B holds Y and wants X, causing both to block forever.

Question 2

Which method allows a thread to pause execution and give other threads a chance to run?

Accepted Answer

Thread.yield()

Answer

Thread.yield() hints to the scheduler that the current thread is willing to relinquish CPU time, though the scheduler may ignore this hint.

Question 3

What does the try-with-resources statement require of its resources?

Accepted Answer

They must implement AutoCloseable

Answer

Resources in try-with-resources must implement AutoCloseable (or its subinterface Closeable), ensuring close() is called automatically.

Question 4

What is the difference between ConcurrentHashMap and Collections.synchronizedMap()?

Accepted Answer

ConcurrentHashMap uses segment-level locking for higher throughput; synchronizedMap locks the entire map per operation

Answer

ConcurrentHashMap uses internal striped locking for much better concurrent throughput, while synchronizedMap serializes all access with a single lock.

Question 5

Which checked exception does Thread.sleep() declare?

Accepted Answer

InterruptedException

Answer

Thread.sleep(millis) declares throws InterruptedException so callers must handle the case where another thread interrupts the sleeping thread.

(1Z0-819) Oracle Java SE 11 Developer Practice Test

(1Z0-819) Oracle Java SE 11 Developer Practice Test

1Z0-819 Exception Handling & Concurrency 4