Java Exercises: Find the area and perimeter of a circle
Java Basic: Exercise-11 with Solution
Write a Java program to print the area and perimeter of a circle.
In geometry, the area enclosed by a circle of radius r is πr2. Here the Greek letter π represents a constant, approximately equal to 3.14159, which is equal to the ratio of the circumference of any circle to its diameter.
The circumference of a circle is the linear distance around its edge.
Pictorial Presentation:

Why is the area of a circle of a circle pi times the square of the radius?

Sample Solution:
Java Code:
public class Exercise11 {
private static final double radius = 7.5;
public static void main(String[] args) {
double perimeter = 2 * Math.PI * radius;
double area = Math.PI * radius * radius;
System.out.println("Perimeter is = " + perimeter);
System.out.println("Area is = " + area);
}
}
Sample Output:
Perimeter is = 47.12388980384689 Area is = 176.71458676442586
Flowchart:

Sample Solution:
Java Code:
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner io = new Scanner(System.in);
System.out.println("Input the radius of the circle: ");
double radius = io.nextDouble();
System.out.println("Perimeter is = " + (2 * radius * Math.PI));
System.out.println("Area is = " + (Math.PI * radius * radius));
}
}
Sample Output:
Input the radius of the circle: 5 Perimeter is = 31.41592653589793 Area is = 78.53981633974483
Flowchart:

Java Code Editor:
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Java: Tips of the Day
countOccurrences
Counts the occurrences of a value in an array.
Use Arrays.stream().filter().count() to count total number of values that equals the specified value.
public static long countOccurrences(int[] numbers, int value) { return Arrays.stream(numbers) .filter(number -> number == value) .count(); }
Ref: https://bit.ly/3kCAgLb
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