If I enter it with a comma (eg 3.5), it works well.
package metodosnumericos;
import java.util.Scanner;
public class derivada {
public static void main(String[] args)
{
//int coeficiente, potencia,x,xc,xp;
Scanner entrada = new Scanner (System.in);
double a;
System.out.println("Ingresa");
// a=Double.parseDouble(entrada.nextLine());
a=entrada.nextDouble();
System.out.println(a);
}
}
Estimated nextDouble() uses the decimal points and separators of thousands of the language.
In Spanish the point is separator of miles and comma the decimales .
Try using the useLocale () function and pass an English Locale, as follows:
entrada.useLocale(Locale.ENGLISH);
You can do it this way, replacing Scanner with BufferedReader and getting line by line.
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Scanner;
public class Derivada {
public static void main(String[] args) throws IOException {
BufferedReader teclado = new BufferedReader(new InputStreamReader(System.in));
double a = 0d;
System.out.println("Ingresa un valor: ");
a = Double.parseDouble(teclado.readLine());
//Se interpreta que teclado.readLine(), obtiene el texto escrito hasta que se pulsa enter
System.out.println(a);
}
}
Check it out, I think it should work.