To my understanding，thefollowingcodeshouldhaveprinttrue，sincebothstreamanditeratorarepointingtothefirstelement。
However，wheniranthefollowingcodeitisprintingfalse :
final HashMap map=new HashMap (；
map.put(a )、b )；
finalsetset=collections.unmodifiablemap (map ).entrySet )；
Map.Entry entry1=set.iterator ().next )；
Map.Entry entry2=set.stream ().findFirst ).get )；
watcouldbethereasonforthisdifferentbehavior？
bothentriesarereferringtothesamelogicalentryofyourmap (whosekeyis ' a ' andvalueis ' b ' ).However，they are not the same insame
ifyoudigdeepenoughintheimplementationofcollections.unmodifiablemap (map )。 you ' llseethatiteratingovertheentrysetofthemapreturnedbycollections.unmodifiablemap (map ) returnsanewmap.entrywhichwraprap
公共地图. entry next (
returnnewunmodifiableentry (I.next )；
}
I ' massuminganewinstancemap.entryinstanceisalsocreatedwhenyoucallset.stream (.findfirst ).get )，sothetwomethood
even if you ' llcallthesamethodtwiceyou ' llgetdifferenceinstances，I.e.thefollowingcodewillalsoprintfalse 3360
Map.Entry entry1=set.iterator ().next )；
Map.Entry entry2=set.iterator ().next )；
On the other hand，ifyouobtaintheentrydirectlyfromtheoriginalhashmap，you will get true:
Map.Entry entry1=map.entrySet ().iterator ).next )；
map.entry entry2=map.entryset (.stream ).findFirst ).get )；
ifthiscasetheentryisnotwrappedbyanewinstance，sobothentryset(.iterator ).next ) (and entrySet ).stream ) ()