El método nextDouble() de la clase java.util.Scanner escanea el siguiente token de la entrada como un Double. Si la traducción es exitosa, el escáner avanza más allá de la entrada que coincidió.
Sintaxis:
public double nextDouble()
Parámetros: La función no acepta ningún parámetro.
Valor devuelto: esta función devuelve el doble escaneado de la entrada.
Excepciones: la función lanza tres excepciones como se describe a continuación:
- InputMismatchException: si el siguiente token no coincide con la expresión regular doble o está fuera de rango
- NoSuchElementException: se lanza si la entrada está agotada
- IllegalStateException: se lanza si este escáner está cerrado
Los siguientes programas ilustran la función anterior:
Programa 1:
// Java program to illustrate the
// nextDouble() method of Scanner class in Java
// without parameter
import java.util.*;
public class GFG1 {
public static void main(String[] argv)
throws Exception
{
String s = "Gfg 9 + 6 = 12.0";
// create a new scanner
// with the specified String Object
Scanner scanner = new Scanner(s);
while (scanner.hasNext()) {
// if the next is a Double,
// print found and the Double
if (scanner.hasNextDouble()) {
System.out.println("Found Double value :"
+ scanner.nextDouble());
}
// if no Double is found,
// print "Not Found:" and the token
else {
System.out.println("Not found Double() value :"
+ scanner.next());
}
}
scanner.close();
}
}
Producción:
Not found Double() value :Gfg Found Double value :9.0 Not found Double() value :+ Found Double value :6.0 Not found Double() value := Found Double value :12.0
Programa 2: Para demostrar InputMismatchException
// Java program to illustrate the
// nextDouble() method of Scanner class in Java
// InputMismatchException
import java.util.*;
public class GFG1 {
public static void main(String[] argv)
throws Exception
{
try {
String s = "Gfg 9 + 6 = 12.0";
// create a new scanner
// with the specified String Object
Scanner scanner = new Scanner(s);
while (scanner.hasNext()) {
// if the next is a Double
// print found and the Double
// since the value 60 is out of range
// it throws an exception
System.out.println("Next Double value :"
+ scanner.nextDouble());
}
scanner.close();
}
catch (Exception e) {
System.out.println("Exception thrown: " + e);
}
}
}
Producción:
Exception thrown: java.util.InputMismatchException
Programa 3: Para demostrar NoSuchElementException
// Java program to illustrate the
// nextDouble() method of Scanner class in Java
// NoSuchElementException
import java.util.*;
public class GFG1 {
public static void main(String[] argv)
throws Exception
{
try {
String s = "Gfg";
// create a new scanner
// with the specified String Object
Scanner scanner = new Scanner(s);
// Trying to get the next Double value
// more times than the scanner
// Hence it will throw exception
for (int i = 0; i < 5; i++) {
// if the next is a Double,
// print found and the Double
if (scanner.hasNextDouble()) {
System.out.println("Found Double value :"
+ scanner.nextDouble());
}
// if no Double is found,
// print "Not Found:" and the token
else {
System.out.println("Not found Double value :"
+ scanner.next());
}
}
scanner.close();
}
catch (Exception e) {
System.out.println("Exception thrown: " + e);
}
}
}
Producción:
Not found Double value :Gfg Exception thrown: java.util.NoSuchElementException
Programa 4: Para demostrar IllegalStateException
// Java program to illustrate the
// nextDouble() method of Scanner class in Java
// IllegalStateException
import java.util.*;
public class GFG1 {
public static void main(String[] argv)
throws Exception
{
try {
String s = "Gfg 9 + 6 = 12.0";
// create a new scanner
// with the specified String Object
Scanner scanner = new Scanner(s);
// close the scanner
scanner.close();
System.out.println("Scanner Closed");
System.out.println("Trying to get "
+ "next Double value");
while (scanner.hasNext()) {
// if the next is a Double,
// print found and the Double
if (scanner.hasNextDouble()) {
System.out.println("Found Double value :"
+ scanner.nextDouble());
}
// if no Double is found,
// print "Not Found:" and the token
else {
System.out.println("Not found Double value :"
+ scanner.next());
}
}
}
catch (Exception e) {
System.out.println("Exception thrown: " + e);
}
}
}
Producción:
Scanner Closed Trying to get next Double value Exception thrown: java.lang.IllegalStateException: Scanner closed
Referencia: https://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#nextDouble()