用Java序列化长数组的最紧凑的方法

I have many arrays of longs long[] and I need to serialize them and save them to disk for later read, notice that each array has to be modified from time to time, but writes are infrequent while reads are frequent. Usually my application needs only a small number of those loaded into memory at the same time. Edits to each array can happen in batch in memory before the array are stored back to disk. Each array has from hundreds up to a million elements. In my application it is critical that loading the desired arrays into memory happens very fast. and I need t