// area1: David I. Schwartz 1/2000
// find area of circle

public class area1 {
    public static void main(String[] args) {

	// Declare radius r and area A
	// A and r will store floating-point values
	double r;
	double A;

	// Assign a f-p value to r
	// Try other values, like -10. and "abc" to see what Java does
	r = 7.1;
	
	// If r is positive, compute area
	// Otherwise, exit from program

	if( r <= 7.1 ) {
	    
	    // Compute area of circle
	    A = Math.PI*r*r;
	    
	    // Output area to screen
	    System.out.println("The area is: " + A);
	}

	else {
	    System.err.println("What kind of r was that?!?");
	    System.exit(0); // exit program 


	}

    }

}

// Output: 
// The area is: 158.36768566746144