问题
My guess is its a 32-bit/64-bit word (depending on the CPU) per value stored in the array. So it would be array size X 32-bit/64-bit.
In the case of linked lists, it would be twice this to store the reference which points to the next element. So it would be 2 * array size X 32-bit/64-bit.
Is this correct, am I missing anything?
回答1:
Much more. Each element in a linked list has:
- Pointer to next element, pointer to previous element, pointer to item value (12 bytes) + object overhead (around another 12 bytes). Say 24 bytes.
- Each element is not primitive but a wrapper. If every element is different, it will occupy space. For integers say another 16 bytes.
Total: 40 bytes per element.
Don't take this at face value, it's just to give you an idea. If you want precise numbers fire up a memory analysis tool (e.g. Eclipse MAT).
回答2:
I made an experiment on memory consumption of arrays. Here are the results for 20000 ints arrays:
OS: Windows 8 6.2, amd64
JVM: Oracle Corporation Java HotSpot(TM) 64-Bit Server VM 24.0-b56
x | min | avg | max | stddev
total cpu, ms | 7.000000 | 8.250000 | 10.000000 | 0.829156
bytes per LinkedList | 830.48 KB | 830.48 KB | 830.48 KB | 0.50 B
bytes per item | 42.00 B | 42.00 B | 42.00 B | 0.00 B
total cpu, ms | 4.000000 | 6.000000 | 7.000000 | 0.547723
bytes per ArrayList | 416.00 KB | 416.00 KB | 416.00 KB | 0.00 B
bytes per item | 21.00 B | 21.00 B | 21.00 B | 0.00 B
total cpu, ms | 0.000000 | 0.950000 | 1.000000 | 0.217945
byt per TIntArrayList| 105.56 KB | 105.56 KB | 105.56 KB | 0.00 B
bytes per item | 5.00 B | 5.00 B | 5.00 B | 0.00 B
So it's
LinkedList: 42 bytes ArrayList: 21 bytes TIntArrayList: 5 bytes
However if the size of the array list is unknown, the resulting memory consumption due to array reallocation is:
LinkedList: 42 bytes ArrayList: 29 bytes TIntArrayList: 10 bytes
来源：https://stackoverflow.com/questions/19322173/how-much-memory-is-used-when-allocating-an-array-vs-allocating-an-linked-list-in