How to speed up external merge sort in Java

Question

I am writing code for the external merge sort. The idea is that the input files contain too many numbers to be stored in an array so you read some of it and put it into files to

Answer 1

You are sorting integers so you should check out radix sort. The core idea of radix sort is that you can sort n byte integers with n passes through the data with radix 256.

You can combine this with merge sort theory.