Area of Triangle in Java

The area of a triangle in Java can be calculated using basic arithmetic operations and built-in Java features. Java is an object-oriented programming language developers widely use for developing software applications.

Java offers platform independence, vast libraries, and frameworks, making it a popular choice among developers, especially for building robust, scalable, and portable applications for web, enterprise, mobile, and embedded systems.

You can easily compute the area of a triangle in Java. This can be done using formulas such as (base × height) / 2. For example, you can write a Java program that accepts user input for the base and height values and computes the triangle's area with the help of these values.

In this tutorial, we’ll discuss several methods of finding the area of a triangle in Java. Keep reading to know more.

Formulas To Find the Area of a Triangle

Using the base and height

If we know the base (b) and the height (h) of the triangle, we can use the formula:

Area = (b * h) / 2

Using the lengths of three sides (Heron's formula)

If we know the lengths of all three sides (a, b, c), we can use Heron's formula:

Area = sqrt(s * (s - a) * (s - b) * (s - c))

where s = (a + b + c) / 2

Using coordinates of vertices

If we know the coordinates of three vertices (x1, y1), (x2, y2), (x3, y3), we can use the shoelace formula:

Area = 0.5 * |(x1y2 + x2y3 + x3y1) - (x2y1 + x3y2 + x1y3)|

Example 1 – Finding the Area of a Triangle in Java Using the Height and Base of the Triangle

Here is an example of calculating the area of a triangle using the height and base of the triangle (base x height) in Java:

import java.util.Scanner;

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

        System.out.println("Enter the base of the triangle:");
        double base = scanner.nextDouble();

        System.out.println("Enter the height of the triangle:");
        double height = scanner.nextDouble();

        double area = (base * height) / 2;
        System.out.println("The area of the triangle is: " + area);
    }
}

The program begins by importing the Scanner class from java.util package, allowing us to read user input. Next, a class named TriangleAreaCalculator is declared, which contains the main method, serving as the program's entry point.

Inside the main method, an instance of the Scanner class is created and associated with the standard input stream (System.in), enabling input reading. The program then prompts the user to enter the base of the triangle by printing the corresponding message. The entered value is read as a double using the nextDouble() method of the Scanner class and assigned to the base variable.

Similarly, the program prompts the user to enter the height of the triangle, reads the input value as a double, and assigns it to the height variable. The area of the triangle is calculated using the formula (base * height) / 2 and assigned to the area variable.

Finally, the program displays the calculated area of the triangle by printing the concatenation of the string "The area of the triangle is: " with the value of the area variable.

Example 2 – Finding the Area of Triangle in Java Using the Three Sides of the Triangle

Here is an example of calculating the area of a triangle using the lengths of its three sides (Heron's formula) in Java:

import java.util.Scanner;

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

        System.out.println("Enter the length of side a:");
        double a = scanner.nextDouble();

        System.out.println("Enter the length of side b:");
        double b = scanner.nextDouble();

        System.out.println("Enter the length of side c:");
        double c = scanner.nextDouble();

        double s = (a + b + c) / 2;
        double area = Math.sqrt(s * (s - a) * (s - b) * (s - c));
        System.out.println("The area of the triangle is: " + area);
    }
}

In the above example, the program prompts the user to enter the lengths of the triangle's three sides. It reads these values as double using the nextDouble() method of the Scanner class and assigns them to the variables a, b, and c.

Next, it calculates the semi-perimeter of the triangle (s) using the formula (a + b + c) / 2. Then, it applies Heron's formula to calculate the triangle area using the Math.sqrt() function to compute the square root.

Finally, the program displays the calculated area of the triangle by printing the concatenation of the string "The area of the triangle is: " with the value of the area variable.

Example 3 - Finding the Area of a Triangle in Java Using Constructor

Here is an example of calculating the area of a triangle in Java using a constructor:

import java.util.Scanner;

public class Triangle {
    private double base;
    private double height;
    private double area;

    public Triangle (double base, double height) {
        this.base = base;
        this.height = height;
    }

    public void calculateArea() {
        area = (base * height) / 2;
    }

    public double getArea() {
        return area;
    }

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

        System.out.println("Enter the base of the triangle:");
        double base = scanner.nextDouble();

        System.out.println("Enter the height of the triangle:");
        double height = scanner.nextDouble();

        Triangle triangle = new Triangle(base, height);
        triangle.calculateArea();

        System.out.println("The area of the triangle is: " + triangle.getArea());
    }
}

This example defines a Triangle class with private fields for base, height, and area. The class has a constructor that takes the base and height as parameters and assigns them to the corresponding fields.

We also have two methods within the Triangle class: calculateArea() and getArea(). The calculateArea() method calculates the area of the triangle using the formula (base * height) / 2 and stores the result in the area field. The getArea() method returns the value of the area field.

In the main method, we prompt the user to enter the base and height of the triangle and read those values using the Scanner class. Then, we create an instance of the Triangle class, passing the base and height as arguments to the constructor.

Next, we call the calculateArea() method on the triangle object to calculate the area. Finally, we display the calculated area of the triangle using the getArea() method. When the program runs, it asks the user to input the base and height of the triangle, creates a Triangle object, calculates the area using the provided values, and displays the resulting area of the triangle.

Example 4 - Finding Area of Triangle in Java Using User-Defined Method

import java.util.Scanner;

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

        System.out.println("Enter the base of the triangle:");
        double base = scanner.nextDouble();

        System.out.println("Enter the height of the triangle:");
        double height = scanner.nextDouble();

        double area = calculateTriangleArea(base, height);

        System.out.println("The area of the triangle is: " + area);
    }

    public static double calculateTriangleArea(double base, double height) {
        return (base * height) / 2;
    }
}

In this program, we define a class called TriangleAreaCalculator. The main method prompts the user to enter the base and height of the triangle, reads those values using the Scanner class, and assigns them to the variables base and height.

The program then calls the calculateTriangleArea method, passing the base and height as arguments. The calculateTriangleArea method calculates the triangle area using the formula (base * height) / 2 and returns the result.

Finally, the calculated area is stored in the area variable and displayed to the user using the System.out.println statement.

Example 5 - Finding the Area of a Triangle in Java Using Object-Oriented Programming

Here is an example of calculating the area of a triangle in Java using object-oriented programming:

import java.util.Scanner;

public class Triangle {
    private double sideA;
    private double sideB;
    private double sideC;

    public Triangle(double a, double b, double c) {
        sideA = a;
        sideB = b;
        sideC = c;
    }

    public double calculateArea() {
        double s = (sideA + sideB + sideC) / 2;
        return Math.sqrt(s * (s - sideA) * (s - sideB) * (s - sideC));
    }

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

        System.out.println("Enter the length of side A:");
        double sideA = scanner.nextDouble();

        System.out.println("Enter the length of side B:");
        double sideB = scanner.nextDouble();

        System.out.println("Enter the length of side C:");
        double sideC = scanner.nextDouble();

        Triangle triangle = new Triangle(sideA, sideB, sideC);
        double area = triangle.calculateArea();

        System.out.println("The area of the triangle is: " + area);
    }
}

In the above program, we define a Triangle class representing a triangle object. The Triangle class has private fields for sideA, sideB, and sideC, representing the lengths of the triangle's three sides.

The Triangle class has a constructor that takes sideA, sideB, and sideC as parameters and initializes the corresponding fields.

Additionally, the Triangle class has a calculateArea() method that calculates the area of the triangle using Heron's formula: Math.sqrt(s * (s - sideA) * (s - sideB) * (s - sideC)), where s is the semi-perimeter of the triangle.

In the main method, we prompt the user to enter the lengths of the triangle's sides (sideA, sideB, and sideC) and read those values using the Scanner class. We then create a Triangle object by invoking the constructor with the provided side lengths.

Next, we call the calculateArea() method on the triangle object to calculate the area and store the result in the area variable. Finally, we display the calculated area of the triangle using the System.out.println statement.

Example 6 – Finding the Area of a Triangle in Java Using an Interface

Here is an example of calculating the area of a triangle in Java by implementing a Shape interface with an area() method:

import java.util.Scanner;

// Define an interface with an area() method
interface Shape {
    void area();
}

// Triangle class implements the Shape interface
public class Triangle implements Shape {
    private double base;
    private double height;

    // Constructor to initialize base and height
    public Triangle(double base, double height) {
        this.base = base;
        this.height = height;
    }

    // Overridden method to calculate and print the area
    public void area() {
        double result = (base * height) / 2;
        System.out.println("The area of the triangle is: " + result);
    }

    // Main method to execute the program
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.println("Enter the base of the triangle:");
        double base = scanner.nextDouble();

        System.out.println("Enter the height of the triangle:");
        double height = scanner.nextDouble();

        // Create a Triangle object and call area()
        Triangle triangle = new Triangle(base, height);
        triangle.area();
    }
}

In this program, we define a Shape interface with an abstract method area(). The Triangle class implements the Shape interface and provides its own definition for the area() method.

The class also includes a constructor that initializes the base and height of the triangle. Inside the overridden area() method, we calculate the area using the formula (base * height) / 2 and print the result.

In the main method, we use the Scanner class to take input from the user for the base and height of the triangle. After reading the values, we create an instance of the Triangle class and call its area() method to calculate and display the area.

This example demonstrates the concept of abstraction in Java using interfaces while keeping the area calculation logic clean and modular.

Conclusion

The numerous ways of calculating the area of a triangle in Java have been discussed in this tutorial. You must enroll in a certified course if you want to use Java for more advanced functions. You could look for software development courses by upGrad. The courses on upGrad are well-designed for professionals and ensure you develop a holistic understanding of the subject. Enquire today to know more.

FAQs

1. How to find the area of a triangle in Java?

To find the area of a triangle in Java, use the formula (0.5 * base * height). Store base and height as floating-point values, then calculate and print the result using simple arithmetic and System.out.println().

2. What is the formula for area of triangle in Java?

The standard area of triangle formula in Java is:

area = 0.5 * base * height;  

This formula is used in most beginner-level programs for calculating the area when base and height are provided.

3. How to write a Java program to calculate area of triangle?

To write a Java program to calculate the area of a triangle, take base and height as input using Scanner, apply the formula, and display the result. This program helps understand variables, user input, and arithmetic operations.

4. Can I calculate area of triangle in Java using Scanner?

Yes, you can calculate the area of triangle in Java using Scanner by taking user input for base and height, then applying the formula. Scanner allows real-time input from the console, making the program interactive.

5. What data type is best for area of triangle in Java?

Use double for storing base, height, and area in your area of triangle Java program. This ensures precision, especially when working with decimal values or larger dimensions.

6. How to create a method for area of triangle in Java?

You can define a method like double calculateArea(double base, double height) to return the area of triangle. This improves modularity and makes the code reusable for multiple triangle inputs.

7. What is a simple Java program to find area of triangle?

A simple Java program to find area of triangle includes input handling using Scanner, calculation using the area formula, and displaying the result using System.out.println(). It’s ideal for beginners learning input/output and formulas.

8. How does user input work in Java area of triangle program?

Use Scanner to read values for base and height. The user types the input in the console, and the program calculates the area of a triangle in Java based on those values.

9. Can you calculate area using Heron’s formula in Java?

Yes, Heron’s formula can be used in Java when you know all three sides. First, calculate the semi-perimeter, then apply Math.sqrt(s*(s−a)*(s−b)*(s−c)) to find the area. It’s useful for more advanced triangle problems.

10. Is the area of triangle program in Java good for beginners?

Yes, the area of triangle program in Java is a common beginner-level exercise. It teaches user input, data types, basic math, and console output—all essential building blocks in Java development.

11. How to handle invalid input in triangle area program?

To handle invalid input in your Java program for area of triangle, use input validation techniques like checking for negative numbers or catching exceptions when input is not a number. This improves user experience and code robustness.

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