HOWTO · Java
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.
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:
