java程序设计一个s=πR²

Scanner input = new Scanner(System.in);
double R = input.nextDouble();
double S = R * R * 3.14;
System.out.println(S);

一个方法搞定吧
class Calc {

public double s(double r) {
return Math.PI*r*r;
}

public static void main(String[] asrg) {
System.out.println(s(2.7));
}

}

public class Test {

public static double getArea(double r) {
return Math.PI * r * r;

}

public static void main(String[] args) {
double r = 1.2;
System.out.println("the area is: " + Test.getArea(r));
}
}