Quadratic Equation Program in Java

In this post, we will develop a Java program for the quadratic equation. It will find the roots of the given quadratic equation.

A quadratic equation is an equation of the second degree, meaning it contains at least one term that is squared. The standard form of the quadratic equation is ax² + bx + c = 0 where a, b and c are real and a !=0, x is an unknown variable. The nature of roots is determined by the discriminant.

Quadratic formula Java

The discriminant of the Quadratic equation is calculated as b²-4ac.

discriminant(d) = b² - 4*a*c

The nature of the roots are given as,

=> If discriminant>1 then the roots are real and different
=> If discriminant=0 then the roots are real and equal
=> discriminant<1 then the roots are complex and different

For the quadratic equation ax² + bx + c = 0, if we denote the discriminant as d, then their roots

If d>1 then the roots are real and different
root1 = (-b + √d)/2a
root2 = (-b – √d)/2a

If d=0 then both roots are -b/2a

If d<1 then roots are complex and different
root1 = -b/2a + i (√d/2a)
root2 = -b/2a – i (√d/2a)

Java program to find roots of Quadratic Equation

import java.util.Scanner;

public class QuadraticProgram {

   public static void main(String[] args) {

      // declare variables
      int a, b, c;
      int desc ;
      int root1, root2 ;
      int realPart, imaginaryPart;

      // create Scanner class object 
      // to read inputs
      Scanner scan = new Scanner(System.in);
      // read inputs
      System.out.print("Enter coefficients "
		+ "(a, b, and c values): ");
      a = scan.nextInt();
      b = scan.nextInt();
      c = scan.nextInt();

      // display Quadratic equation
      System.out.print("The quadratic equation: ");
      System.out.format("%d*x^2 + %d*x + %d = 0\n",
                  		a, b, c);

      // calculate discriminant
      desc = (b*b) - (4*a*c);

      // find roots
      if(desc > 1) {
         // both roots are real and different 
         root1=(-b+(int)Math.sqrt(desc))/2*a;
         root2=(-b-(int)Math.sqrt(desc))/2*a;
         // display roots
         System.out.println("Roots are = "+ 
	    		root1 + ", "+ root2);
      } 

      else if(desc == 0) {
         // both roots are real and equal 
         root1=(-b+(int)Math.sqrt(desc))/2*a;
         root2 = root1;
         // display roots
         System.out.println("Roots are = "+ 
	    		root1+ ", "+ root2);
      } 

      else {
         // roots are complex and different
         realPart = -b/(2*a);
         imaginaryPart=(int)Math.sqrt(desc)/(2*a);
 	 System.out.format("root1 = %d + i(%d)\n",
			realPart, imaginaryPart);
	 System.out.format("root2 = %d - i(%d)\n",
			realPart, imaginaryPart);
      }

      // close Scanner class object
      scan.close();
   }
}

The output for the different test cases are:-

Enter coefficients (a, b, and c values): 1 -1 -6
The quadratic equation: 1*x^2 + -1*x + -6 = 0
Roots are = 3, -2

Enter coefficients (a, b, and c values): 1 0 -25
The quadratic equation: 1*x^2 + 0*x + -25 = 0
Roots are = 5, -5

Enter coefficients (a, b, and c values): 1 -12 36
The quadratic equation: 1*x^2 + -12*x + 36 = 0
Roots are = 6, 6

Enter coefficients (a, b, and c values): 1 4 5
The quadratic equation: 1*x^2 + 4*x + 5 = 0
root1 = -2 + i(0)
root2 = -2 – i(0)

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