I have a scanner with many lines of text(representing number) and I want to convert all the text in the scanner to a List. Example:
Scanner myScanner = new Scanner(new File("input.txt"));
input.txt:
000110100110
010101110111
111100101011
101101001101
011011111110
011100011001
110010011100
000001011100
101110100110
010001011100
011111001010
100111100101
111111000010
My first thought was to convert it to a String by changing the delimiter to something I know is not in the file:
myScanner.useDelimiter("impossible String");
String content = myScanner.next();
and then use
List<String> fullInput = Arrays.asList(content.split("\n"));
However, it gives me problems later on with parsing the numbers on the scanner. I've tried debugging it but I can't seem to understand the problem. For example, I made it print the String to the console before parsing it. It would print a proper number(asString) and then give me NumberFormatException when it is supposed to parse.
Here's the runnable code:
public static void main(String[] args) throws FileNotFoundException {
Scanner myScanner = new Scanner(new File("input.txt"));
myScanner.useDelimiter("impossible String");
String content = myScanner.next();
List<String> fullInput = Arrays.asList(content.split("\n"));
System.out.println(fullInput.get(1));
System.out.println(Long.parseLong(fullInput.get(1)));
}
This is what I ended up using after the first didn't work:
Scanner myScanner = new Scanner(new File("input.txt"));
List<String> fullInput = new ArrayList<>();
while (sc.hasNextLine())
fullInput.add(myScanner.nextLine());
Do you know what's wrong with the first method or is there a better way to do this?
For what you are trying to do here, Scanner is the wrong solution.
If your goal is to simply read the all lines of the file as String[] you can use the Files.readAllLines(Path, Charset) method (javadoc) to do this. You could then wrap that as a List using Arrays.asList(...).
What you are actually doing could work under some circumstances. But one possible problem is that String.split("\n") only works on systems where the line terminator is a single NL character. On Windows, the line terminator is a CR NL sequence. And in that case, String.split("\n") will leave a CR at the end of all but the last string / line. That would be sufficient to cause Long.parseLong(...) to throw a NumberFormatException. (The parseXxx methods do not tolerate extraneous characters such as whitespace in the argument.)
A possible solution to the extraneous whitespace problem is to trim the string; e.g.
System.out.println(Long.parseLong(fullInput.get(1).trim()));
The trim() method (javadoc) returns a string with any leading and/or trailing whitespace removed.
But there is another way to deal with this. If you don't care whether each number in the input file is on a separate line, you could do something like this:
Scanner myScanner = new Scanner(new File("input.txt"));
List<Long> numbers = new ArrayList<>();
while (myScanner.hasNextLong()) {
numbers.append(myScanner.nextLong());
}
Finally, @ChengThao makes a valid point. It looks like these are binary numbers. If they are in fact binary, then it makes more sense to parse them using Long.parseLong(string, radix) with a radix value of 2. However if you parse them as decimal using parseLong (as you are currently doing) the values in your question will fit into a long type.