How can a garbage collector lose a pointer to a allocated object in memory?

Garbage Collector (GC) in Android (for example, in Dalvik or ART) tracks objects that have references from root objects. If a reference to an object is lost, meaning there are no references pointing to that object, GC considers it unreachable and may free the memory.

A reference to an allocated object can be lost in the following cases:

• The variable holding the reference goes out of scope (for example, a local variable in a method finishes execution).
• The reference is overwritten with a new value, and the old object is no longer accessible.
• The reference is stored in a weak (WeakReference) or soft (SoftReference) reference, which GC can clear.
• Cyclic references, if the collector does not handle them correctly (rare in modern GC).

Thus, if the program no longer holds references to an object, the garbage collector "loses" the reference to it and may free the memory.