In Java memory management, who can actually destroy an object reference x?

Introduction / Context:
Unlike languages with explicit deallocation (e.g., C with free, C++ with delete), Java relies on automatic garbage collection. Understanding what APIs do and do not guarantee is critical for correct reasoning about object lifetime.

Given Data / Assumptions:

• We want to know how object destruction occurs in Java.
• Various APIs and methods are proposed as mechanisms.

Concept / Approach:
Java objects are destroyed only by the garbage collector when they become unreachable from GC roots. Methods like System.gc() or Runtime.getRuntime().gc() merely request a GC; they do not guarantee immediate collection. The finalize() method (now deprecated) is a callback that may run prior to collection; calling it directly does not collect an object. There is no delete() in Java.

Step-by-Step Reasoning:

Verification / Alternative check:
Empirical tests show that calling System.gc() may not trigger a collection or may collect a different set than expected. The JVM chooses timing and strategy.

Why Other Options Are Wrong:
There is no x.delete() in Java; finalize() is not a destructor and calling it manually is incorrect; Runtime.getRuntime().gc() is merely a hint; claims of immediate destruction are false.

Common Pitfalls:
Assuming GC is deterministic; relying on finalize() for resource management instead of try-with-resources/close.

Final Answer:
Only the garbage collection system can destroy an object.