What is a garbage collector?

Automatic memory management mechanism that frees unused objects in the heap.

Principles of operation:

• Reachability determination of objects: Tracks objects referenced by live (accessible) objects from roots (e.g., thread stacks).
• Releasing unreachable objects: Objects with no references are considered "garbage" and their memory can be reused.

Types of garbage collectors (depend on language/platform):

• Mark and Sweep: Marks reachable objects (marking), then traverses the heap and frees unmarked objects (cleaning). Can lead to memory fragmentation.
• Copying: Divides the heap into two parts. Copies live objects to a new part, then cleans the old one. Prevents fragmentation but requires more memory.
• Generational: Divides objects by age into generations. Most garbage collection occurs in the "young" generation, where most objects have short lifespans.

Advantages:

• Reduces the likelihood of memory leaks.
• Simplifies development (no need to explicitly free memory).

Disadvantages:

• Can cause delays (pauses) during program execution during collection.
• Unpredictable collection time.