Implementation of the algorithm solving a quadratic equation in Java

import static java.lang.Math.sqrt;
import java.util.Scanner;
public class Square {
  public static void main(String[] args) {
    double a,b,c;
    Scanner key=new Scanner(System.in);
    System.out.print("a=");
    a=key.nextFloat();
    System.out.print("b=");
    b=key.nextFloat();
    System.out.print("c=");
    c=key.nextFloat();
    if(a==0) 
      linear(b,c);
    else{
      double delta;
      delta=b*b-4*a*c;
      if(delta<0)
        System.out.println("lack of solutions");
      else
      if(delta==0){
        double x;
        x=-b/(2*a);
        System.out.print("x = ");
        System.out.println(x);
      }
      else{
        double x1, x2;
        x1=(-b+sqrt(delta))/(2*a);
        x2=(-b-sqrt(delta))/(2*a);
        System.out.print("x1 = ");
        System.out.println(x1);
        System.out.print("x2 = ");
        System.out.println(x2);
      }
    }
  }
  static void linear(double a, double b){
    if(a==0)
      if(b==0)
        System.out.println("identity equation");
      else
        System.out.println("contrary equation");
    else{
      double x;
      x=-b/a;
      System.out.print("linear equation, x = ");
      System.out.println(x);
    }
  }
}