A reachable object cannot be garbage collected. Only unreachable objects may be garbage collected.

No, an object cannot be garbage collected while it is still reachable. In Java, the garbage collector is responsible for reclaiming memory occupied by objects that are no longer reachable or referenced by any live part of the program. If an object is still reachable, it means that there is at least one reference to it from a live part of the program, and as a result, it will not be eligible for garbage collection.

Reachability is determined by the reachability analysis performed by the Java Virtual Machine (JVM). Objects that are not reachable from the root of the object graph (such as local variables, static variables, etc.) are considered eligible for garbage collection.

In summary, an object must be unreachable from the root of the object graph to be eligible for garbage collection. If it is still reachable, it will not be collected by the garbage collector.