Manual input works, reading from txt file causes infinite loop java

Question

I apologize in advance for the similarity between this question and many others, but after checking through and trying solutions from other questions, I've yet to solve my issue. The following is test code provided for testing the SAP class from the princeton assignment wordnet(found here http://www.cs.princeton.edu/courses/archive/fall14/cos226/assignments/wordnet.html )

public static void main(String[] args) {
In in = new In(args[0]);
Digraph G = new Digraph(in);
SAP sap = new SAP(G);
while (!StdIn.isEmpty()) {
    int v = StdIn.readInt();
    int w = StdIn.readInt();
    int length   = sap.length(v, w);
    int ancestor = sap.ancestor(v, w);
    StdOut.printf("length = %d, ancestor = %d\n", length, ancestor);
}
}

For some reason, using this test code gives me an infinite loop when I try to pass text files (an example txt file can be found here: ftp://ftp.cs.princeton.edu/pub/cs226/wordnet/digraph1.txt).

Since this code was given to me by the assignment page, I assume that its right. This leads me to question, could something else in my code be causing an infinite loop? I'm unsure of what to check besides the while loop of this test code.

In addition, am I some how passing the text file wrong? The steps that I took to pass digraph1.txt were

Run -> Run configurations for the SAP class

and then for arguments I put in ${file_prompt} and chose the digraph1.txt each time.

When I manually enter in the digraph1.txt all of my methods work perfectly fine.

Thanks in advance!