map - Java : Iteration through a HashMap, which is more efficient? -

given following code, 2 alternative ways iterate through it,
is there performance difference between these 2 methods?

        map<string, integer> map = new hashmap<string, integer>();         //populate map          //alt. #1         (string key : map.keyset())         {             integer value = map.get(key);             //use key , value         }          //alt. #2         (map.entry<string, integer> entry : map.entryset())         {             string key = entry.getkey();             integer value = entry.getvalue();             //use key , value         } 

i inclined think alt. #2 more efficient means of iterating through entire map (but wrong)

your second options more efficient since doing lookup once compared n number of times in first option.

but, nothing sticks better trying out when can. here goes -

(not perfect enough verify assumptions , on machine anyway)

public static void main(string args[]) {      map<string, integer> map = new hashmap<string, integer>();     // populate map      int mapsize = 500000;     int strlength = 5;     for(int i=0;i<mapsize;i++)         map.put(randomstringutils.random(strlength), randomutils.nextint());      long start = system.currenttimemillis();     // alt. #1     (string key : map.keyset()) {         integer value = map.get(key);         // use key , value     }     system.out.println("alt #1 took "+(system.currenttimemillis()-start)+" ms");      start = system.currenttimemillis();     // alt. #2     (map.entry<string, integer> entry : map.entryset()) {         string key = entry.getkey();         integer value = entry.getvalue();         // use key , value     }     system.out.println("alt #2 took "+(system.currenttimemillis()-start)+" ms"); } 

results (some interesting ones)

with int mapsize = 5000; int strlength = 5;
alt #1 took 26 ms
alt #2 took 20 ms

with int mapsize = 50000; int strlength = 5;
alt #1 took 32 ms
alt #2 took 20 ms

with int mapsize = 50000; int strlength = 50;
alt #1 took 22 ms
alt #2 took 21 ms

with int mapsize = 50000; int strlength = 500;
alt #1 took 28 ms
alt #2 took 23 ms

with int mapsize = 500000; int strlength = 5;
alt #1 took 92 ms
alt #2 took 57 ms

...and on