I'm working on a school project.

I'm trying to gather data from a .txt file with Scanner but I get an error when I want to use the Scanner to initiate variable.

My code

File etudiant = new File("./data/etudiants.txt");
File personnel = new File("./data/personnel.txt");
Scanner scEtudiant = new Scanner(etudiant);
Scanner scPersonnel = new Scanner(personnel);

//creation liste etudiant
while (scEtudiant.hasNextLine()) {
    int num = scEtudiant.nextInt();
    String nom = scEtudiant.next();
    String prenom = scEtudiant.next();
    String telephone = scEtudiant.next();
    String email = scEtudiant.next();
    int annee = scEtudiant.nextInt();

    individuListe.put(num, new Etudiant(num, nom, prenom, telephone, email, annee));
}
scEtudiant.close();

My error

Exception in thread "main" java.util.NoSuchElementException
at java.base/java.util.Scanner.throwFor(Scanner.java:937)
at java.base/java.util.Scanner.next(Scanner.java:1594)
at java.base/java.util.Scanner.nextInt(Scanner.java:2258)
at java.base/java.util.Scanner.nextInt(Scanner.java:2212)
at gestion.Gala.<init>(Gala.java:37)
at gestion.Main.main(Main.java:7)

If I remove the variable and put some System.out.println() instead it display the data properly but still outputs this error.

CodePudding user response：

Read and analyze the stacktrace

The error-output / stacktrace shows invocation of Scanner.nextInt() as causing the NoSuchElementException. See line 37 of your code, where nextInt() was called, probably one of those two:

• int num = scEtudiant.nextInt();
• int annee = scEtudiant.nextInt();

Learn about NoSuchElementException

This exception is thrown by all next..() methods in class Scanner. It indicates that the expected next token (here of numerical type Int) was not found in the scanned text-stream.

See JavaDoc of nextInt() for Throws description:

Throws:

InputMismatchException - if the next token does not match the Integer regular expression, or is out of range

NoSuchElementException - if input is exhausted

IllegalStateException - if this scanner is closed

To prevent this Exception when calling next..() methods you can test on the presence of a next element with hasNext(), hasNext..() or hasNextLine() predicate-methods.

See also:

• Baeldung tutorial: Java Scanner hasNext() vs. hasNextLine()

Robust solution: Prevent the error with guard statements

use hasNextInt() to test if there is a next element of type int and so on.

while (scEtudiant.hasNextLine()) { // each student record on a new line
    if (!scEtudiant.hasNextInt()) { // guard breaks loop if no int
        break;
    }
    int num = scEtudiant.nextInt();

    if (!scEtudiant.hasNext()) { // guard breaks loop if no String
        break;
    }
    String nom = scEtudiant.next();
    
    if (!scEtudiant.hasNext()) { // guard breaks loop if no String
        break;
    }
    String prenom = scEtudiant.next();
    
    String telephone = ""; // not available, default to empty
    if (scEtudiant.hasNext()) { // optional: if string available 
       telephone = scEtudiant.next();
    }
    
    String email = ""; // not available, default to empty
    if (scEtudiant.hasNext()) { // optional: if string available 
       email = scEtudiant.next();
    }

    if (!scEtudiant.hasNextInt()) { // guard breaks loop if no int
        break;
    }
    int annee = scEtudiant.nextInt();

    var etudiant = new Etudiant(num, nom, prenom, telephone, email, annee)
    individuListe.put(etudiant.getNum(), etudiant);
}

CodePudding user response：

You are not sharing the whole class for that reason I can not say for sure but can guess that you are not giving the default values to the primitive variables in the while loop. So what you should do first declare them outside the function give them default value and then use it inside while loop

CodePudding user response：

Change the while loop condition to scEtudiant.hasNextInt()?

Typically you use a hasNextXXX method of Scanner before the corresponding nextXXX method.