You don't need to. If a file has been redirected to your program and there's stuff in it, then System.in will have a handle it. If there's nothing in the System.in buffer, then you can assume no file has been passed to you.
Joined: May 25, 2005
I wan to design my program in the way that user can use redirection to read in file
java program < input.txt
if the user enter command java program, the program will display "Enter file name:" from there, the user will key in the file name.
how do System.in detect there's no file redirection instead?
It doesn't matter. Just write the program as if there's someone there typing. If input is coming from a pipe instead, then the prompts will be printed, but no-one will read them. They'll just be ignored.
Hi, I tried just the following code but do not work. I would like the program to skip the User input if file redirection is used. or skip file redirection and request for user input if command "java program" is used.