Why Does My Java Thread Remain Uncollected Even After Setting Its Reference to Null?

Java Thread Garbage Collection: Explained

Despite the thread's "null" reference in line B, it continues to run due to its status as a garbage collection root. The garbage collector (GC) determines "reachability" based on these roots.

Understanding GC Roots

Running threads are considered GC roots, rendering objects referenced by them "reachable" and thus preventing their garbage collection. This principle also applies to the main thread, which remains ungarbage collected despite its lack of references.

Example Analysis

In the provided code, the anonymous thread created in line A becomes a GC root upon execution. Line B sets its reference to "null" but does not terminate the thread, which continues running endlessly due to its GC root status. As long as the main thread runs, the GC cannot collect the thread object, explaining its persistent existence.

Conclusion

Running threads effectively prevent garbage collection of any objects they reference. This behavior ensures the integrity of executing code and prevents unexpected memory leaks. The notion of GC roots is crucial in understanding Java's memory management and the interplay between threads and garbage collection.

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