java - Having issues with project euler 23 (loops) -

for reason, having trouble loop in first method of code, ans. if @ while , while loops, while loop working fine, running through each element in linkedhashset, though do-while stops after while has had first run through. num1 doesn't move passed 12, while num2 becomes every value in set, , not sure why. figured out printing num1 , num2, , unable figure out why happening. , appreciated. here code:

import java.util.set; import java.util.linkedhashset; import java.util.iterator; public class main{ public static int ans(set<integer> abund,int total){     int sum;     object num1;     object num2;     iterator itr=abund.iterator();//creates iterator values set     do{//loop values set         num1=itr.next();//assigns each object in set num         while (itr.hasnext()){//loop values set add             num2=itr.next();//assigns each object in set num             sum=((int) num1+(int) num2);             total-=sum;         }     }while (itr.hasnext());     return total; }  public static boolean abun(int y){     int x;     int facsum=0;     for(x=1;x<y;x++){         if (y%x==0){             facsum+=x;         }     }     if (facsum>y){         return true;     }     else{         return false;     } }  public static void main(string[] args){     int x;//for loop counter     int y;//another loop counter     int total=0;//total of numbers 0-28123     int fin;//final answer     boolean abundant;     set<integer> abund=new linkedhashset<integer>();     (x=0;x<28124;x++){         abundant=abun(x);         if (abundant==true){             abund.add(x);         }         total+=x;     }     fin=ans(abund,total);     system.out.println("final: "+fin);  } } 

thanks

you need build sums of pairs set of abundant numbers a, a_i <= a_j. cannot execute nested loop using single iterator, which, definition, goes first last. it's difficult use 2 iterators or foreach loops, since inner loop must skip position outer loop holds. therefore...

use list hold abundant numbers iteration:

public static int ans(list<integer> abund, int total){     for( int = 0; < abund.size(); ++i ){         for( int j = i; j < abund.size(); ++j ){             total -= abund.get(i) + abund.get(j);         }     }     return total; }  set<integer> abund=new hashset<integer>();  // list-arraylist fin = ans( new arraylist( abund ), total ); 

actually, using list enough, since numbers different anyway.