El método nextBoolean() de la clase java.util.Scanner escanea el siguiente token de la entrada como un valor booleano. Si la traducción es exitosa, el escáner avanza más allá de la entrada que coincidió.
Sintaxis:
public boolean nextBoolean()
Parámetros: La función no acepta ningún parámetro.
Valor devuelto: esta función devuelve el valor booleano escaneado de la entrada.
Excepciones: la función lanza tres excepciones como se describe a continuación:
- InputMismatchException: si el siguiente token no es un booleano válido
- 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
// nextBoolean() 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 true 9 + 6 = 12.0 false";
// create a new scanner
// with the specified String Object
Scanner scanner = new Scanner(s);
while (scanner.hasNext()) {
// if the next is a Boolean,
// print found and the Boolean
if (scanner.hasNextBoolean()) {
System.out.println("Found Boolean value :"
+ scanner.nextBoolean());
}
// if no Boolean is foucnd,
// print "Not Found:" and the token
else {
System.out.println("Not found Boolean() value :"
+ scanner.next());
}
}
scanner.close();
}
}
Producción:
Not found Boolean() value :Gfg Found Boolean value :true Not found Boolean() value :9 Not found Boolean() value :+ Not found Boolean() value :6 Not found Boolean() value := Not found Boolean() value :12.0 Found Boolean value :false
Programa 2: Para demostrar InputMismatchException
// Java program to illustrate the
// nextBoolean() 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 Boolean
// print found and the Boolean
// since the value 60 is out of range
// it throws an exception
System.out.println("Next Boolean value :"
+ scanner.nextBoolean());
}
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
// nextBoolean() 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 Boolean value
// more times than the scanner
// Hence it will throw exception
for (int i = 0; i < 5; i++) {
// if the next is a Boolean,
// print found and the Boolean
if (scanner.hasNextBoolean()) {
System.out.println("Found Boolean value :"
+ scanner.nextBoolean());
}
// if no Boolean is found,
// print "Not Found:" and the token
else {
System.out.println("Not found Boolean value :"
+ scanner.next());
}
}
scanner.close();
}
catch (Exception e) {
System.out.println("Exception thrown: " + e);
}
}
}
Producción:
Not found Boolean value :Gfg Exception thrown: java.util.NoSuchElementException
Programa 4: Para demostrar IllegalStateException
// Java program to illustrate the
// nextBoolean() 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 Boolean value");
while (scanner.hasNext()) {
// if the next is a Boolean,
// print found and the Boolean
if (scanner.hasNextBoolean()) {
System.out.println("Found Boolean value :"
+ scanner.nextBoolean());
}
// if no Boolean is found,
// print "Not Found:" and the token
else {
System.out.println("Not found Boolean value :"
+ scanner.next());
}
}
}
catch (Exception e) {
System.out.println("Exception thrown: " + e);
}
}
}
Producción:
Scanner Closed Trying to get next Boolean value Exception thrown: java.lang.IllegalStateException: Scanner closed
Referencia: https://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#nextBoolean()