Написать условие для данной программы

class strana{
public strana(){
stran str=new stran(15,"Rasha","Moskau",3);
stran tav2=new stran(300,"USA","Washington",9);
str.show();
tav2.show();
str.sum();
av strn3 = new av(15,"Rasha","Moskau",5,100,"Volgograd");
strn3.goroda();
str strn =new str(15,"Rasha","Moskau",5,100,"Eurasia",5);
str strn2=new str(200,"USA","Washington",10,200,"Severnaya Amerika",3);
strn.plos();
strn2.plos();}
public static void main(String[] arg){
new strana();}}
class stran{
double narod;
String naimenovanie;
String capital;
double pl;
stran( double s,String m,String t,double sr){
narod=s;
naimenovanie=m;
capital=t;
pl=sr;}
void show(){
System.out.println("Strana:  " + naimenovanie);
System.out.println("Naselenie:  " + narod + " mln");
System.out.println("Ploshad:  " + pl + " mln \n");}
void sum(){
double s=0, k=0, p=0;
s=pl*1000000;
k=narod*1000000;
p=s/k;
System.out.println("Plotnost: " + Math.round(p*10));}}
class av extends stran{
private int zenapr;
private String gorod;
av(int s,String m,String t,int sr,int pc,String pok){
super( s, m, t, sr);
zenapr=pc;
gorod=pok;}
void goroda(){
System.out.println("Gorod: "+gorod);}}
class str extends av{
int plo;
str(int sa,String ma,String t,int asr,int pca,String pok,int kl){
super( sa, ma,t, asr,pca,pok);
plo=kl;}
void plos(){
System.out.println("Ploshad: " + plo);}}