Double-Checked Locking / Locking Correctness in Multithreaded Code

In a multithreaded environment, implement/fix shared object initialization to be thread-safe while minimizing locking overhead. Requirements Implement getInstance() for a singleton: create on first call, return the same instance afterwards. Discuss and avoid classic double-checked locking pitfalls (e.g., reordering causing a partially constructed object to be observed). What to cover What is a correct implementation under the target language/memory model (e.g., Java/C++)? Alternative approaches (static init, Initialization-on-demand holder, CAS, etc.). Example Input 100 threads concurrently call getInstance() 1000 times each Output all returned references should be identical