# How to solve a Quadratic Equation in Java ?.

In this Java tutorial, you will learn how to solve Quadratic equation through a Java program. In this Java tutorial, you will encounter a video tutorial which will demonstrate how to solve Quadratic equation step-by-step. Below there is complete Java source code along with steps to implement the same. At last there is output of the program.

## What is a Quadratic Equation ?.

## Video tutorial - How to solve Quadratic Equation in Java ?.

Below is the video tutorial, which demonstrate how to solve Quadratic Equation in Java step-by-step.

// Step 1 - Import Scanner class from the package // java.util. Before using Scanner class nextDouble // method, you have to import Scanner class. import java.util.Scanner; public class QuadraticEquationDemo { public static void main(String[] args) { // Step 2 - Create a Scanner class instance using // new operator and calling Scanner constructor. // The constructor takes in System.in inputstream // as a parameter to it. System.in helps Scanner // class to read user inputs from the Java console. Scanner input = new Scanner(System.in); // Step 3 - Create 5 variables of datatype double. // These variables take in values of constants used in // quadratic equation such as - a , b , c , d ,discriminant. // All these variables are initialized to zero. These variables // hold values entered by the user later. double a = 0; double b = 0; double c = 0; double d = 0; double discriminant = 0; // Step 4 - Prompt the user to enter the value of constant a. System.out.print("Enter the value of constant a : "); // Step 5 - a holds the value entered by the user on Java console. // Scanner class has a method by name nextDouble(). This method // reads double value entered by user on the Java console and // assign it to a variable. a = input.nextDouble(); // Step 6 - Prompt the user to enter the value of constant b. System.out.print("Enter the value of constant b : "); // Step 7 - b holds the value entered by the user on Java console. // Scanner class has a method by name nextDouble(). This method // reads double value entered by user on the Java console and // assign it to b variable. b = input.nextDouble(); // Step 8 - Prompt the user to enter the value of constant c. System.out.print("Enter the value of constant c : "); // Step 9 - c holds the value entered by the user on Java console. // Scanner class has a method by name nextDouble(). This method // reads double value entered by user on the Java console and // assign it to c variable. c = input.nextDouble(); // Step 10 - Calculate discriminant of quadratic equation by using // following formula - // discriminant = (b * b - 4 * a * c) discriminant = (b * b - 4 * a * c); // Step 11 - Calculate the value of d by using following formula - // d = square root of discriminant. // Math class has a static method by name sqrt(). This method // returns square root of number passed to it as parameter. d = Math.sqrt(discriminant); // Step 12 - Here, if discriminant comes out to be greater than // quadratic equation has two roots calculated by formula - // roots = + ( -b + d ) / ( 2.0 * a )) // else roots of quadratic equation are not real numbers. if (discriminant >= 0.0) { System.out.println("First root of the Quadratic equation is : " +(-b + d) / (2.0*a)); System.out.println("Second root of the Quadratic equation is : " +(-b - d) / (2.0*a)); } else { System.out.println("The roots are not real numbers."); } } }

## Steps to implement -

**Step 1** - Import Scanner class from the package java.util. Before using Scanner class nextDouble method, you have to import Scanner class.

**Step 2** - Create a Scanner class instance using new operator and calling Scanner constructor. The constructor takes in System.in inputstream as a parameter to it. System.in helps Scanner class to read user inputs from the Java console.

**Step 3** - Create 5 variables of datatype double. These variables take in values of constants used in quadratic equation such as - a , b , c , d ,discriminant. All these variables are initialized to zero. These variables hold values entered by the user later.

**Step 4** - Prompt the user to enter the value of constant a.

**Step 5** - 'a' holds the value entered by the user on Java console. Scanner class has a method by name nextDouble(). This method reads double value entered by user on the Java console and assign it to 'a' variable.

**Step 6** - Prompt the user to enter the value of constant b.

**Step 7** - 'b' holds the value entered by the user on Java console. Scanner class has a method by name nextDouble(). This method reads double value entered by user on the Java console and assign it to 'b' variable.

**Step 8** - Prompt the user to enter the value of constant c.

**Step 9** - 'c' holds the value entered by the user on Java console. Scanner class has a method by name nextDouble(). This method reads double value entered by user on the Java console and assign it to 'c' variable.

**Step 10** - Calculate discriminant of quadratic equation by using

following formula - **discriminant = (b * b - 4 * a * c) **

**Step 11 - **Calculate the value of d by using following formula -** d = square root of discriminant.**Math class has a static method by name sqrt(). This method returns square root of number passed to it as parameter.

**Step 12** - Here, if discriminant comes out to be greater than quadratic equation has two roots calculated by formula - **roots = + ( -b + d ) / ( 2.0 * a ))**

else roots of quadratic equation are not real numbers.

## Output of the program -

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