Reading from a File in Java in intelliJ

It's not the issue, that the file could not be found in IntelliJ. It's the fact, that your compiler says, that the file could possible not found at runtime. So you have to handle the FileNotFoundException with a try-catch block around like this:

try { BufferedReader reader = new BufferedReader(new FileReader("./input.txt")); // read the file // ... } catch (FileNotFoundException e) { // do something, when the file could not be found on the system System.out.println("The file doesn't exist."); } catch (IOException e) { // do something, when the file is not readable System.out.println("The file could not be read."); } catch (/* other exceptions... */) { // do something else on some other exception // ... } 

Of course, you already know, that the file will be found, but not the compiler!

Basically read about Exceptions: http://docs.oracle.com/javase/tutorial/essential/exceptions/

You should either specify the full path to the file or run the program so that its working directory contains this file. The second can be achieved if you go to your run configuration settings and ensure that Working DIrectory field is pointing to Hexagram directory.

You can also throw the FileNotFoundException into your main method, your output just won't be as pretty.

public static void main(String[] args) throws FileNotFoundException {