为什么我的方法不能从文件中读取每个值？

Question

public static int getBoys(ArrayList<String> boysNames, Scanner s) throws IOException {
    // Getting boys file location
    System.out.println("Please enter the file name containing the the boys names.");
    String boyFileLocation = s.nextLine();

    // Opening the file containing the names of boys
    File boyFile = new File(boyFileLocation);
    Scanner BF = new Scanner(boyFile);
    int initialBoyCount = 0;
    int i = 0;
    boysNames.add(BF.nextLine());

    while (BF.hasNextLine()) {
        if (BF.nextLine().equals(boysNames.get(i))) {

        } else {
            boysNames.add(BF.nextLine());
            initialBoyCount++;
            i++;
            System.out.println(boysNames.get(i));
        }
    }

    return (initialBoyCount);
}

I am trying to read in from a file a list of names and add them to an array list. However there are duplicates of certain names and i am only suppoused to keep the unique ones (If if already exists don't add it again). However, I figured out that it is only giving me every other name. Starting with 2, and giving me the following errors.

Exception in thread "main" java.util.NoSuchElementException: No line found
    at java.util.Scanner.nextLine(Scanner.java:1540)
    at namesList.namesList.getBoys(namesList.java:53)
    at namesList.namesList.main(namesList.java:27)

Answer 1

The reason of the exception in this line

if (BF.nextLine().equals(boysNames.get(i))) 

you read a line and if equation isn't true in else branch you call BF.nextLine() again. So sometimes you read line twice but you call hasNextLine() only once .

Solution: read line only one time before if statement.