How much additional memory is allocated when calling the LinkedList.add() method?

When calling LinkedList.add(E element), memory is allocated for one new node (Node). Each node stores:

• A reference to the next node (next).
• A reference to the previous node (prev).
• The data of the element (item).

The total additional memory depends on the size of the stored element E, the size of references (depends on JVM architecture, usually 4 or 8 bytes), and overheads for the Node object (object header). An approximate calculation:

• Size of Node: (size of next reference) + (size of prev reference) + (size of item) + (overhead of Node object).

For example, for a JVM with 64-bit architecture (8-byte references) and storing an Integer object:

• Size of reference: 8 bytes.
• Size of Integer: about 16 bytes (the object itself + header).
• Overhead of Node: about 16 bytes.

Total: 8 + 8 + 16 + 16 = 48 bytes. This is an approximate value; the exact size may vary.

When calling LinkedList.add(int index, E element), memory is also allocated for one new node, similar to add(E element). Additional temporary variables used for searching the position in the list allocate minimal memory on the stack and are released after the method completes.