java中麻烦给我个简单的正方形求面积的编程?

package test;
import java.util.Scanner;
public class Test
{
public static void main( String[] args )
{
Scanner s = new Scanner( System.in );
System.out.println( "请输入边长" );
double n = s.nextDouble();
System.out.println( "面积是:" + n * n );
}
}