java - Can program execution go different by choosing between Enhanced for loop and old fashioned index based loop for a collection? -

i asked in interview. said no. interviewer did not seem impressed.

any corner case missed?

note: not talking cases 1 can iterate 2 times faster/modify loop variable.

in other words difference between

for (int = 0;i<set.size();i++) { // } 

and

for (int x : set) { // something. } 

anything performance(i know both compile same code)/etc.

the answer is: yes, program may behave differently.

kayaman mentioned thread-safety in answer. special case may show different behavior. question whether or not collection itself modified during iteration 1 aspect may influence program flow.

but regardless of that, enhanced for-loop, iterator created @ beginning of loop. , iterator keep reference "his" collection iterating over. in contrast that, iteration classical for-loop take account when collection replaced new one.

this can seen in following example.

import java.util.arraylist; import java.util.list;  public class differentforloops {     public static void main(string[] args)     {         differentforloops d = new differentforloops();         d.startold();         d.startnew();     }      private list<integer> list;      private void createlist(int size)     {         list = new arraylist<integer>();         (int i=0; i<size; i++)         {             list.add(i);         }     }      public void startold()     {         createlist(10);          (int = 0;i<list.size();i++)         {             system.out.println("old: entry "+list.get(i)+" of "+list);             pause();              list = list.sublist(0, list.size()-1);         }             }      public void startnew()     {         createlist(10);          (int : list)         {             system.out.println("new: entry "+a+" of "+list);             pause();              list = list.sublist(0, list.size()-1);         }             }      private static void pause()     {         try         {             thread.sleep(500);         }         catch (interruptedexception e)         {             thread.currentthread().interrupt();         }     }  }