研究: さまざまな種類の JVM ガベージ コレクション メカニズム

public void mark(Object obj) {
    if (obj.isMarked) {
        return;
    }
    obj.isMarked = true;
    for (Object ref : obj.references) {
        mark(ref);
    }
}

public void markSweep() {
    mark(rootObject);
    for (Object obj : heap) {
        if (!obj.isMarked) {
            sweep(obj);
        } else {
            obj.isMarked = false;
        }
    }
}

public void sweep(Object obj) {
    obj.references.clear();
    heap.remove(obj);
}

public void copy() {
    for (Object obj : heap) {
        if (obj.isMarked) {
            copyToSurvivorSpace(obj);
        }
    }
}

public void copyToSurvivorSpace(Object obj) {
    if (obj.isCopied) {
        return;
    }
    obj.isCopied = true;
    SurvivorSpace.add(obj);
    for (Object ref : obj.references) {
        copyToSurvivorSpace(ref);
    }
}

public void swap() {
    Object[] temp = fromSpace;
    fromSpace = toSpace;
    toSpace = temp;
}

public void clear() {
    toSpace.clear();
}

public void compact() {
    int newIndex = 0;
    for (int i = 0; i < heap.length; i++) {
        Object obj = heap[i];
        if (obj.isMarked) {
            obj.isMarked = false;
            heap[newIndex++] = obj;
        } else {
            sweep(obj);
        }
    }
}

public void swap() {
    for (Object obj : heap) {
        for (Field field : obj.fields) {
            if (field.getValue().isObject()) {
                field.getValue().updateReference();
            }
        }
    }
}

public void sweep(Object obj) {
    obj.references.clear();
    heap.remove(obj);
}