The formula for finding the area of a rectangle is,

area = length * width

Calculate Area of a Rectangle in Java

The following program calculates area of a rectangle in Java. The program asks the user for length and width values and then outputs the result in the console. We use BufferedReader to read a line of string and then use the parseDouble method of the Double class to convert the string to a number.

This program also illustrates the decorator pattern. We first decorate the console input stream (System.in) with a InputStreamReader and then again decorate it with BufferedReader. BufferedReader enables us to read a line of data from an input stream.

// Java program to find area of a rectangle
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class RectangleArea {
    
    public static void main(String[] args) throws IOException{
        
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        System.out.print("Please enter length of the rectangle : ");
        double length = Double.parseDouble(reader.readLine());
        
        System.out.print("Please enter width of the rectangle : ");
        double width = Double.parseDouble(reader.readLine());
        
        System.out.println("Area of the rectangle : "+length*width);
        
    }
    
}