Excepción en Thread Main Java.Util.NoSuchElementException: No se encontró ninguna línea

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Sheeraz Gul 12 octubre 2023
Java Java Exception
Excepción en Thread Main Java.Util.NoSuchElementException: No se encontró ninguna línea

Este tutorial demuestra cómo resolver la Excepción en el subproceso "principal" java.util.NoSuchElementException: No se encontró ninguna línea en Java.

Excepción en el subproceso "principal" java.util.NoSuchElementException: no se encontró ninguna línea

La excepción java.util.NoSuchElementException es una excepción no verificada en tiempo de ejecución. La JVM genera esta excepción cuando usamos métodos como next(), nextElement(), iteradores o métodos o enumeraciones.

El error Excepción en el hilo "principal" java.util.NoSuchElementException: No se encontró ninguna línea ocurre cuando estamos usando un Escáner para obtener la entrada del usuario con métodos como nextLine(); el error ocurrirá cuando intentemos usar el método sin ningún límite.

Probemos un ejemplo que demuestra este error.

package delftstack;

import java.util.Scanner;

public class Example {
  static boolean[][] Articles;
  public static void main(String[] args) {
    // This initiates all array values to be false
    Articles = new boolean[4][4];
    for (int i = 0; i < 4; i++) {
      for (int j = 0; j < 4; j++) {
        Articles[i][j] = false;
      }

      // Welcome message
      System.out.println("-------------------------");
      System.out.println("Welcome to Delftstack.com.");
      System.out.println("-------------------------\n");

      // Starts program
      Programstart();
    }
  }

  public static void Programstart() {
    // to read users' input
    Scanner sc = new Scanner(System.in);

    // user input
    String Requested_Lanuguage;
    String Requested_Article;

    // Counters for articles array
    int Count_Language = 0;
    int Count_Artciles = 0;

    // User to select their choice of Programming Language
    System.out.print("Please type 1 for Java or 2 for Python: ");

    // Language preference
    Requested_Lanuguage = sc.nextLine();

    switch (Requested_Lanuguage) {
      case "1":
        // User selects Java
        System.out.println(">>> You have selected Java. \n");
        break;

      case "2":
        // User selects Python
        System.out.println(">>> You have selected Python. \n");
        break;

      default:
        // User has not selected a valid Programming Language
        System.out.println(">>> You have not selected a valid choice. Please try again. \n");
        Programstart();
        break;
    }

    // user to select their choice of article
    System.out.print("Please type 1 for Web and 2 for App: ");

    // Article preference
    Requested_Article = sc.nextLine();

    switch (Requested_Article) {
      case "1":
        // User selects Web Articles
        System.out.println(">>> You have selected Web Articles. \n");
        break;

      case "2":
        // User selects App Articles
        System.out.println(">>> You have selected App Articles. \n");
        break;

      default:
        // User has not selected a valid article
        System.out.println(">>> You have not selected a choice. Please try again. \n");
        Programstart();
        break;
    }

    // Closes Scanner
    sc.close();
  }
}

La salida para el código anterior es:

-------------------------
Welcome to Delftstack.com.
-------------------------

Please type 1 for Java or 2 for Python: 1
>>> You have selected Java.

Please type 1 for Web and 2 for App: 1
>>> You have selected Web Articles.

Exception in thread "main" -------------------------
Welcome to Delftstack.com.
-------------------------

Please type 1 for Java or 2 for Python: java.util.NoSuchElementException: No line found
    at java.base/java.util.Scanner.nextLine(Scanner.java:1651)
    at delftstack.Example.Programstart(Example.java:45)
    at delftstack.Example.main(Example.java:24)

El error ocurre porque usamos el método nextLine() sin ningún límite. Para solucionar este problema necesitamos reemplazar el código Requested_Article = sc.nextLine(); al siguiente código.

while (sc.hasNextLine()) {
  Requested_Article = sc.nextLine();
  // Switch condition here
}

Probemos la solución.

package delftstack;

import java.util.Scanner;

public class Example {
  static boolean[][] Articles;
  public static void main(String[] args) {
    // This initiates all array values to be false
    Articles = new boolean[4][4];
    for (int i = 0; i < 4; i++) {
      for (int j = 0; j < 4; j++) {
        Articles[i][j] = false;
      }

      // Welcome message
      System.out.println("-------------------------");
      System.out.println("Welcome to Delftstack.com.");
      System.out.println("-------------------------\n");

      // Starts program
      Programstart();
    }
  }

  public static void Programstart() {
    // to read users' input
    Scanner sc = new Scanner(System.in);

    // user input
    String Requested_Lanuguage;
    String Requested_Article;

    // Counters for articles array
    int Count_Language = 0;
    int Count_Artciles = 0;

    // User to select their choice of Programming Language
    System.out.print("Please type 1 for Java or 2 for Python: ");

    // Language preference
    Requested_Lanuguage = sc.nextLine();

    switch (Requested_Lanuguage) {
      case "1":
        // User selects Java
        System.out.println(">>> You have selected Java. \n");
        break;

      case "2":
        // User selects Python
        System.out.println(">>> You have selected Python. \n");
        break;

      default:
        // User has not selected a valid Programming Language
        System.out.println(">>> You have not selected a valid choice. Please try again. \n");
        Programstart();
        break;
    }

    // user to select their choice of article
    System.out.print("Please type 1 for Web and 2 for App: ");

    // Article preference
    while (sc.hasNextLine()) {
      Requested_Article = sc.nextLine();

      switch (Requested_Article) {
        case "1":
          // User selects Web Articles
          System.out.println(">>> You have selected Web Articles. \n");
          break;

        case "2":
          // User selects App Articles
          System.out.println(">>> You have selected App Articles. \n");
          break;

        default:
          // User has not selected a valid article
          System.out.println(">>> You have not selected a choice. Please try again. \n");
          Programstart();
          break;
      }
    }
    // Closes Scanner
    sc.close();
  }
}

El código anterior no arrojará la Excepción en el hilo "principal" java.util.NoSuchElementException: No se encontró línea ahora. Ver la salida:

-------------------------
Welcome to Delftstack.com.
-------------------------

Please type 1 for Java or 2 for Python: 1
>>> You have selected Java.

Please type 1 for Web and 2 for App: 1
>>> You have selected Web Articles.

1
>>> You have selected Web Articles.


>>> You have not selected a choice. Please try again.

Please type 1 for Java or 2 for Python:
Autor: Sheeraz Gul
Sheeraz Gul avatar Sheeraz Gul avatar

Sheeraz is a Doctorate fellow in Computer Science at Northwestern Polytechnical University, Xian, China. He has 7 years of Software Development experience in AI, Web, Database, and Desktop technologies. He writes tutorials in Java, PHP, Python, GoLang, R, etc., to help beginners learn the field of Computer Science.

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