Multiple processes share the same output/input streams

I wrote a java program to start a C program as a process and I create many processes of that C program that are worki开发者_StackOverflowng simultaneously. Each process log its output to a different file. It worked well but the problem is that when one process flush an output it is written in all the log files which means that all process share the same output/input streams

Is there a way to separate each process output/input stream so that they don't log to all files?