DaM

public static void main(String[] args) {       int r=10;               for(int y=0;y<=2*r;y++){                    for(int x=0;x<=2*r;x++){                        if(((x-r)*(x-r))+((y-r)*(y-r))==r*r){                            System.out.print("*");                        }                        else{                            System.out.print("  ");                        }                    }                    System.out.println("");               }    }