Error in java second degree equation algorithm

Question

Good morning, could someone help me understand why my code is not doing the correct processing and why my conditional deviation is wrong?

public void cap4ex3e(){
    double a,b,c,delta,x1,x2;
    Scanner in = new Scanner(System.in);
    a = in.nextFloat();
    b = in.nextFloat();
    c = in.nextFloat();
    if ((a!=0)&&(b!=0)&&(c!=0)){
        delta = Math.sqrt(b)-4*a*c;
        if (delta<0) {
            System.out.println("Não há solução real");
        } else if (delta>0){
            x1=(-b+Math.pow(delta,1/2))/(2*a);
            x2=(-b-Math.pow(delta,1/2))/(2*a);
            System.out.println("Há duas soluções reais: "+x1+"e"+x2);
        } else {
            x1=(-b+Math.pow(delta,1/2))/(2*a);
            x2=(-b-Math.pow(delta,1/2))/(2*a);
            System.out.println("Há apenas uma solução real: "+x1+"e"+x2);
        }
         System.out.println("Não é uma equação do 2º grau");
    }
}

When I assign the positive values to the variables a, b and c it falls into the conditional deviation

if (delta<0) {
    System.out.println("Não há solução real"); 

and:

System.out.println("Não é uma equação do 2º grau");

What wasn’t supposed to happen.

I believe it’s the way out in the wrong place of the condition but I can’t see it.

Answer 1

The delta calculation is wrong, it must be

currently stands as

Note that the last message

It’s not a second-degree equation

is being shown always, I imagine that some validation of when to show it or not.

And also that in the part where there is only one real solution, the solution is printed twice.

I made some adjustments to the code, to make it more readable. In general, the error is only in the formula that calculates the delta.

import java.util.Scanner;

class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);

        double a, b, c;
        try {
            a = in.nextDouble();
            b = in.nextDouble();
            c = in.nextDouble();
        } finally {
            in.close();
        }

        if(a == 0 || b == 0 || c == 0) {
            System.out.println("A, B e C precisam ser diferentes de zero");
            return;
        }

        double delta = (b * b) - (4 * a * c);
        double x1, x2;

        if (delta < 0) {
            System.out.println("Não há solução real");
        } else if (delta > 0){
            x1 = (-b + Math.pow(delta, 1/2)) / (2 * a);
            x2 = (-b - Math.pow(delta, 1/2)) / (2 * a);
            System.out.println("Há duas soluções reais: " + x1 + " e " + x2);
        } else {
            x1 = (-b + Math.pow(delta, 1/2)) / (2 * a);
            x2 = (-b - Math.pow(delta, 1/2)) / (2 * a);
            System.out.println("Há apenas uma solução real: " + x1 + " e " + x2);
        }
    }
}

See working on repl.it