java.util.NoSuchElementException: No line found ; error when I have a new variable each time for input

Question

I'm trying to run my program in a loop and it runs perfectly fine the first time, but once it loops over and tries to find the nextLine, it crashes. My only issue with this is that I have a variable that is assigned by scanner.nextLine() then it delimits it. Shouldn't it ask for input every time instead of erroring?

private static List<String> readInput()
   {

      ArrayList<String> inputtedWords = new ArrayList<String>(); // creates an ArrayList called inputtedWords
      Scanner kb = new Scanner(System.in); //creating a scanner kb (keyboard)

      System.out.println("Text: "); // user input for Text:

      String fullText = kb.nextLine(); 
      Scanner s = new Scanner(fullText).useDelimiter(" "); //parses the fullText string and separates them on spaces

      while(s.hasNext()) // loops until their is not another word 
      {
         String tempStr = s.next();
         if (!Character.isAlphabetic(tempStr.charAt(tempStr.length()-1)))
            tempStr = tempStr.substring(0, tempStr.length()-1);

         inputtedWords.add(tempStr);
      }
      s.close();//closing scanners
      kb.close();//closing scanners
      return inputtedWords; // returns the inputtedWords list
   }

This is the code for the beginning of the loop...

List<String> dictionary = readDictionary(); // creates a List called dictionary and sets it equal to the file in method "readDictionary"

      while (done) // Change this to a while loop and negate it.  Remember to get another line of input at the end of the loop.
      {

         List<String> inputtedWords = readInput(); // creates another List for the words inputted into the method "readInput"
         if ((inputtedWords.size() == 1) && (inputtedWords.get(0).equals("done")))
         {
             done = false;
            System.out.println("Exiting Program");
            continue;
         }

      for  (String newWord : inputtedWords) // newWord = word inputted
      { // beginning of for loop, initializes element as a string then searches loops through the length of inputtedWords

         List<String> possibleAnswers = new ArrayList<>(); //creates an ArrayList called "possibleAnswers" 
         possibleAnswers.add(newWord); // adds the newly created word into the possibleAnswers list

         List<String> characters = new ArrayList<String>(); // creates another ArrayList called "chars"

I've been working on a fix for this for a while but cannot seem to figure out why it's erroring on me.

Answer 1

On you code,

private static List<String> readInput(){
    //Your other code here 
    Scanner kb = new Scannr(System.in); //creating a scanner kb (keyboard)

    //Your other code here
    String fullText = kb.nextLine(); // read from user input
    //Your other code here

}

this Error was encountered due to the loop here

while (done){
    List<String> inputtedWords = readInput();
    //Your other code here 
}

base on Oracle documentation for Java here. And I quote:

public String nextLine() Advances this scanner past the current line and returns the input that was skipped. This method returns the rest of the current line, excluding any line separator at the end. The position is set to the beginning of the next line. Since this method continues to search through the input looking for a line separator, it may buffer all of the input searching for the line to skip if no line separators are present.

Returns: the line that was skipped

Throws: NoSuchElementException - if no line was found

It is recommended to add kb.hasNextLine() as validation to avoid the exception.

private static List<String> readInput(){
    //Your other code here 
    Scanner kb = new Scannr(System.in); //creating a scanner kb (keyboard)

    //Your other code here
    String fullText =  kb.hasNextLine() ? kb.nextLine() :""; // read from user input with validation

    //Or you can use. Use only one of these codes.
    String fullText = ""; // read from user input with validation
    if(kb.hasNextLine()){
         fullText = kb.nextLine();
    }
    //Your other code here

}

But you might get an infinite loop from that code.

You can solve the infinite loop by moving the variable of kb into static class attribute like

private static Scanner kb = null;
private static List<String> readInput(){
    //Your other code here 
    //kb = new Scannr(System.in); creating a scanner kb (keyboard) ***REMOVE this line***
    Scanner s = new Scanner(fullText).useDelimiter(" "); //parses the fullText string and separates them on spaces. ***This should be fine to where it is.****

    //Your other code here
    String fullText = kb.nextLine(); // read from user input
    //Your other code here
    s.close();//closing scanners  ***This should be fine to where it is.****
    //kb.close();  closing scanners ***REMOVE this from here***
}

Then move innitialization of scanner and kb.close(); outside your loop. like:

kb = new Scannr(System.in);
while (done){
    List<String> inputtedWords = readInput();
    //Your other code here 
}
kb.close();  closing scanner

If you don't want scanner as static attribute of the class, you can just send scanner as argument of the method like:

private static List<String> readInput(Scanner kb){

    //Your other code here
    String fullText =  kb.hasNextLine() ? kb.nextLine() :""; // read from user input with validation

    //Your other code here

}

On your loop

Scanner kb = new Scannr(System.in);
while (done){
    List<String> inputtedWords = readInput(kb);
    //Your other code here 
}
kb.close();  closing scanner

Answer 2

Moving the kb.close() outside of the loop fixed the whole thing.