Circle.java

public class Circle{
	private double radius;
	
	public Circle(double radius){
		if(radius > 0){
			this.radius = radius;
		}
		else{
			System.out.println("Invalid radius value.Radius value must be greater than 0.");
		}
	}
	
	public double getRadius(){
		return radius;
	}
	
	public void setRadius(double radius){
		if(radius > 0){
			this.radius = radius;
		}
		else{
			System.out.println("Invalid radius value.Radius value must be greater than 0.");
		}
	}
	
	public double calculateArea(){
		return Math.PI * radius * radius;
	}
	
	public double calculatePerimeter(){
		return 2 * Math.PI * radius;
	}	
}

/////////////////////////////////////////////
////////////////////////////////////////////

TestCircle.java

public class TestCircle{
	
	public static void main(String args[]){
		
		Circle circle = new Circle(5);
		
		System.out.println("Radius: " + circle.getRadius());
		System.out.printf("Area: %.2f\n" , circle.calculateArea());
		System.out.printf("Perimeter: %.2f\n" , circle.calculatePerimeter());
		
		circle.setRadius(8);
		
		System.out.println("Updated Radius: " + circle.getRadius());
		System.out.printf("Updated Area: %.2f\n" , circle.calculateArea());
		System.out.printf("Updated Perimeter: %.2f\n" , circle.calculatePerimeter());
		
		circle.setRadius(-3);
		
		
	}
	
}