How does the garbage collector detect objects that are eligible for removal from memory?

Garbage collector in Android (specifically in Java/Kotlin environment) identifies objects to be deleted using several main methods:

1. Reference Counting — tracks the number of references to an object. If there are no references, the object is considered unused. However, this method does not handle cyclic references.

2. Reachability Graph Traversal (Tracing Garbage Collection) — the collector starts from root objects (stack, static variables) and marks all reachable objects. Objects that are not marked are considered unreachable and are eligible for deletion.

3. Various Garbage Collection Algorithms — such as Mark-and-Sweep, Generational GC, which optimize the process of identifying and removing unnecessary objects.

In Android, tracing GC is predominantly used, which periodically runs to clean memory of objects that are no longer referenced by active code.