What methods are you familiar with for identifying objects that are subject to deletion by the automatic garbage collection system?

In Java, the main approaches for identifying objects to be garbage collected are:

1. Reachability — an object is considered reachable if there is a reference to it from root objects (GC Roots), such as local variables in the stack, static fields, active threads, etc. If an object is unreachable, it is considered a candidate for removal.

2. Mark-and-Sweep — the collector first marks all reachable objects, then removes the unmarked ones.

3. Reference Counting — less common in JVM, but the idea is that an object is removed when there are no more references to it.

4. Using special references (WeakReference, SoftReference, PhantomReference) — objects referenced through such references can be removed under certain conditions.

Example: if an object is not accessible from the stack or static fields, it will be collected by the garbage collector.