FormulaGeneral.java

import java.util.Scanner;

class FormulaGeneral {
  static Scanner sn = new Scanner(System.in);

  private static double askNumber(String question) {
    double userInput = 0;
    while (true) {
      System.out.print(question);
      try {
        userInput = Double.parseDouble(sn.next());
        break; // will only get to here if input was a double
      } catch (NumberFormatException ignore) {
        System.out.print("Intenta de nuevo. ");
      }
    }
    return userInput;
  }

  public static void main(String[] args) {
    // obtenemos los valores de los coeficientes
    double a = askNumber("Ingresa el coeficiente a: ");
    double b = askNumber("Ingresa el coeficiente b: ");
    double c = askNumber("Ingresa el coeficiente c: ");
    
    // resolvemos la raiz y revisamos si la solución es un numero real
    double insideSquareRoot = Math.pow(b, 2) - (4 * a * c);
    if (insideSquareRoot < 0) {
      System.out.println("La solución no es real.");
    } else {
      double x1 = ((-b + Math.sqrt(insideSquareRoot)) / (2 * a));
      double x2 = ((-b - Math.sqrt(insideSquareRoot)) / (2 * a));
      System.out.println(String.format("El valor de x1 es: %s, el valor de x2 %s.", x1, x2));
    }
  }
}