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• ArrayList:

  • Backed by a dynamic array.
  • Fast random access with O(1) time complexity for get operations.
  • Insertion and deletion operations are slower (O(n)) because elements need to be shifted.

• LinkedList:

  • Implemented as a doubly linked list.
  • Insertion and deletion are faster (O(1)) when working with nodes (if the node reference is known).
  • Slower random access (O(n)) as it needs to traverse the list to access elements.

Explanation: You need to understand when to use each based on performance characteristics and application requirements.

• == Operator:

  • Compares the memory addresses (references) of objects.
  • Used to check if two references point to the same object.

• equals() Method:

  • Defined in the Object class but can be overridden to compare the content of the objects.
  • Often overridden in custom classes to provide logical equality checks (e.g., comparing values rather than references).

Explanation: Understanding these differences is crucial for ensuring accurate comparisons in Java programs.

• Java Memory Model (JMM):

  • Defines how threads interact through memory and how changes to memory are visible to other threads.
  • Ensures visibility, ordering, and atomicity of operations.

• Garbage Collection:

  • Automatic memory management process that reclaims memory used by objects that are no longer reachable.
  • Common algorithms include Mark-and-Sweep, Generational GC, and G1 (Garbage-First).

Explanation: A solid understanding of the Java memory model and garbage collection helps in writing efficient, thread-safe code.

• Checked Exceptions:

  • Subclasses of Exception but not RuntimeException.
  • Must be either caught or declared in the method signature using throws.

• Unchecked Exceptions:

  • Subclasses of RuntimeException.
  • Not required to be caught or declared; typically result from programming errors (e.g., NullPointerException).

• Error:

  • Represents serious issues that are usually not handled by applications (e.g., OutOfMemoryError).

Exception Handling: – Use try, catch, and finally blocks to handle exceptions. – Use custom exceptions to handle application-specific scenarios.

Explanation: Proper exception handling is crucial for building robust and fault-tolerant applications.

• Multithreading:

  • Allows concurrent execution of two or more threads to improve application performance.

• Synchronization:

  • Ensures that only one thread can access a resource or a section of code at a time.
  • Achieved using the synchronized keyword or higher-level concurrency utilities like ReentrantLock.

Explanation: Understanding multithreading and synchronization is essential for developing efficient, thread-safe applications.