Calculate circle area. (#5644)

core-java/src/main/java/com/baeldung/area/circle/Circle.java

@@ -0,0 +1,30 @@
+package com.baeldung.area.circle;
+
+public class Circle {
+
+    private double radius;
+
+    public Circle(double radius) {
+        this.radius = radius;
+    }
+
+    public double getRadius() {
+        return radius;
+    }
+
+    public void setRadius(double radius) {
+        this.radius = radius;
+    }
+
+    public double getArea() {
+        return calculateArea();
+    }
+
+    private double calculateArea() {
+        return radius * radius * Math.PI;
+    }
+
+    public String toString() {
+        return "The area of the circle [radius = " + radius + "]: " + calculateArea();
+    }
+}

core-java/src/main/java/com/baeldung/area/circle/CircleArea.java

@@ -0,0 +1,36 @@
+package com.baeldung.area.circle;
+
+import java.util.InputMismatchException;
+import java.util.Scanner;
+
+public class CircleArea {
+
+    public static void main(String[] args) {
+        if (args.length > 0) {
+            try {
+                double radius = Double.parseDouble(args[0]);
+                calculateArea(radius);
+            } catch (NumberFormatException nfe) {
+                System.out.println("Invalid value for radius");
+                System.exit(0);
+            }
+        }
+
+        try (Scanner scanner = new Scanner(System.in)) {
+            System.out.println("Please enter radius value: ");
+            double radius = scanner.nextDouble();
+            calculateArea(radius);
+        } catch (InputMismatchException e) {
+            System.out.println("Invalid value for radius");
+            System.exit(0);
+        }
+
+        Circle circle = new Circle(7);
+        System.out.println(circle);
+    }
+
+    private static void calculateArea(double radius) {
+        double area = radius * radius * Math.PI;
+        System.out.println("The area of the circle [radius = " + radius + "]: " + area);
+    }
+}