public class RecursionGroups
{
    
public RecursionGroups(){

System.out.println("countDown(4)  : " + countDown(4));

System.out.println("printHi(5) : " + printHi(5) );

System.out.println("printPerfectSquares(5) : " + printPerfectSquares(5) );


System.out.println("doubleString(4,\"Java\") : "+ doubleString(4,"Java") );
}


//Group 1
public String countDown(int fromWhere){
if(fromWhere == 1)
    return "1 ," ;   
else
 return fromWhere +" , "+ countDown(fromWhere-1);

}



//Group 2
public String printHi(int howManyTimes){
if(howManyTimes == 1)
    return "Hi," ;   
else
 return "Hi, " +  printHi(howManyTimes-1);

}


//Group 3
public String printPerfectSquares(int howMany){
if(howMany == 2)
    return "4," ;   
else
 return  howMany * howMany + ", " +  printPerfectSquares(howMany-1);

}
 



//Group 4
public String doubleString(int howManyTimes, String str){
    if(howManyTimes  == 1)
        return str ;
    else
        return  str + doubleString( howManyTimes - 1,str) ;

}





}