Section 4.3 Garbage Collection
Garbage Collection is a fundamental concept in computer programming, particularly in languages like Java. It is the process of automatically reclaiming memory that is no longer in use by the program, freeing it up for future allocations. Garbage collection plays a vital role in memory management, ensuring efficient resource utilization and preventing memory leaks.
When a program executes, it dynamically allocates memory to hold objects, variables, and other data structures. As the program runs, the garbage collector periodically examines the objects to determine which ones are still in use. It does this through a process called "mark and sweep." It starts by traversing the reachable objects (e.g., through global variables, static variables, and local variables, etc.), marking all objects in use. Any objects not marked during this traversal are considered unreachable and eligible for garbage collection. When we lose all references to an object it becomes unreachable and so it will be garbage collected.
After marking all reachable objects, the garbage collector performs the sweep phase. It frees the memory occupied by objects that were not marked as reachable. This memory is then returned to the available memory pool for future allocations.
In some garbage collection algorithms, an additional step called compaction may be performed. Compaction involves moving the live objects closer together, effectively defragmenting memory. This can improve memory access performance.
Garbage collection alleviates the burden of manual memory management, where programmers would have to explicitly allocate and deallocate memory for objects. By automating memory reclamation, garbage collection reduces the risk of memory leaks and simplifies the development process. It is essential to be mindful of object lifetimes and design memory-efficient programs that optimize garbage collection performance.
