How is automatic garbage collection implemented when searching for objects in memory management algorithms?

Automatic garbage collection (Garbage Collection, GC) in languages like Java is implemented through algorithms that find and free memory occupied by objects that are no longer referenced.

The main idea is to find reachable objects from root points (root set), such as local variables, static fields, etc. All objects that can be reached via reference chains from the roots are considered alive. The rest are garbage and can be removed.

An example algorithm is a depth-first or breadth-first traversal of the object graph, starting from the roots, to mark live objects. Then, memory occupied by unmarked objects is freed.

In Java, a generational collector is often used, which divides objects into generations (young, old) and optimizes collection, as most objects quickly become garbage.

An example of simplified pseudocode for finding live objects:

void markReachableObjects(Set<Object> roots) {
    Set<Object> reachable = new HashSet<>();
    Deque<Object> stack = new ArrayDeque<>(roots);
    while (!stack.isEmpty()) {
        Object obj = stack.pop();
        if (!reachable.contains(obj)) {
            reachable.add(obj);
            for (Object ref : obj.getReferences()) {
                stack.push(ref);
            }
        }
    }
    // All objects not in reachable are considered garbage
}