Java Mastermind: The Ultimate Challenge for Experienced Developers Quiz

1. Question 1: Thread Coordination in Concurrency

   Which advanced Java concurrency utility would be most appropriate for implementing a reusable barrier that allows a fixed number of threads to wait for each other at a common point before proceeding, as in a multi-phase computation?

   1. A. CyclicBarrier
   2. B. CountDownLatch
   3. C. Semaphore
   4. D. ThreadGroup
   5. E. ForkJoinPool

2. Question 2: The JVM Memory Model

   In the Java Virtual Machine memory structure, which area is specifically used for storing per-thread information such as the program counter, local variables, and operand stacks, but is not shared among threads?

   1. A. Java Heap
   2. B. Method Area
   3. C. Java Stack
   4. D. MetaSpace
   5. E. CodeCache

3. Question 3: NIO Buffer Operations

   When working with a java.nio.ByteBuffer, which of the following method calls switches the buffer from writing mode to reading mode by setting the limit to the current position and resetting the position to zero?

   1. A. rewind()
   2. B. clear()
   3. C. slice()
   4. D. flip()
   5. E. compact()

4. Question 4: equals() and hashCode() Contract

   If you override the equals(Object o) method in a Java class but do not override the hashCode() method, what is the likely consequence when using instances of this class as keys in a HashMap?

   1. A. The program will fail to compile
   2. B. The equals() method will work but hash collisions will never occur
   3. C. HashMap operations like get() and put() may behave unpredictably
   4. D. The class will throw a NullPointerException at runtime
   5. E. The JVM will automatically generate a correct hashCode()

5. Question 5: Lambda Expressions and Effective Final

   In Java 8 and above, what requirement must a local variable meet for it to be referenced inside a lambda expression, as in the following example:nnRunnable r = () -u003E System.out.println(count);

   1. A. It must be explicitly declared as static
   2. B. It must be transient
   3. C. It must be synchronized
   4. D. It must be effectively final
   5. E. It must be a class-level variable