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copied!<p>Your problem here is only tangentially associated with knowing how to use modulus. You have one master function doing a mess of things: initializing variables, opening files, iterating through rows, and figuring out display parameters. This is known as procedural programming, and bad procedural programming at that: you want to leverage object oriented programming here.</p> <pre><code>//note the standards regarding class names: Capitalize Class Names! //also, pick names that make it clear what you're doing. public class DisplayTimes { DataInputStream in; //This is not actually the correct way to do this, but it's lightweight enough for this example List<Integer> runnerIds = new ArrayList<Integer>(); List<Integer> runnerMinutes = new ArrayList<Integer>(); List<Integer> runnerSeconds = new ArrayList<Integer>(); //note that your main method should not throw an exception. Nothing can catch it!! //also note that this is just an entry point; it probably shouldn't do any work public static void main(String[] args) { DisplayTimes display = new DisplayTimes("c:\\java\\chapter13\\sheet2\\program2.jdat2"); display.readAndDisplay(); } //constructors are the proper way to initialize object variables public DisplayTimes(String inputFile) { //see how much easier this next line is to read? this.in = new DataInputStream(new FileInputStream(fileName)); } public void readAndDisplay() { processData(); //offload processing somewhere else System.out.println("Runner\tTotal \tTotal \tTime"); System.out.println("Number\tMinutes\tSeconds\tBehind\n"); for (int idx = 0; idx++; idx<runnerIds.size()) { String output = runnerIds.get(idx)+"\t"; output = output + runnerMinutes.get(idx)+"\t"; output = output + runnerSeconds.get(idx)+"\t"; output = output + calculateDifference(idx)+"\t"; System.out.println(output); } } private void processData() { boolean moreData = true; while (moreData) { //offload the work of the loop to another method moreData = processRunner(); } } private boolean processRunner() { try { int id=in.readInt(); in.readChar();//how is this file formatted that you need to skip a char? int mins=in.readInt(); in.readChar(); int secs=in.readInt(); //Here you should really sanity-check your values //Instead we'll just store them this.runnerIds.add(id); this.runnerMinutes(mins); this.runnerSeconds(secs); return isFinished(); } catch (EOFException e) { //Exceptions should NOT be used for program control. //They should be used when there is bad data. System.out.println("There was an unexpected termination of the datafile."); } } private boolean isFinished() { in.mark(1); if (in.read == -1) {//checks cleanly if we're at the end of the file. return false; } else { in.reset();//moves you back to mark return true; } } private String calculateDifference(int idx) { if (idx == 0) { return "\t"; } //First runner is first! int previousTimeInSeconds = (runnerMinutes.get(idx-1) * 60) + runnerSeconds.get(idx-1); int nextTimeInSeconds = (runnerMinutes.get(idx) * 60) + runnerSeconds.get(idx); int delta = (nextTimeInSeconds - previousTimeInSeconds); return (delta / 60) + "min " + (delta % 60) + "sec \t"; } } </code></pre> <p>The main thing you should take away here is that the problem you came here with - calculating the difference between runner a and b - is only a small part of the code you presented. You couldn't present a <a href="http://sscce.org/" rel="nofollow">Short, Self Contained, Correct (Compilable), Example</a> because your code was improperly tangled with other code. By writing clean code you can focus on the one function (<code>calculateDifference()</code>) that you actually needed help with. While I understand you may be beginning and working out of a book (based on what was presented), the most fundamental thing you can learn is how to break down a problem into the smallest pieces possible. Utilize the language to help you with this; don't fight it.</p>

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