Java方法4-4练习，烦请老师检查和指正～

package imooc_redo_exercise;

public class AreaDemo {
		public double area(double r) {
			double area = Math.PI * r * r;
			return area;
		}

		public int area(int a, int b) {
			int area = a * b;
			return area;
		}

		public static void main (String args[]) {
			AreaDemo ad = new AreaDemo();
			double r = 4.5;
			int a = 8,  b = 5;
			System.out.println("The area of a circle is: " + ad.area(r));
			System.out.println("The area of a rectangle is: " + ad.area(a, b));

		}

}