HashMap java.util.ConcurrentModificationException -

i have following code:

public list<string> processmap(map<string, string> amap) {     cloner cloner = new cloner();      map<string, string> tempmap = cloner.deepclone(amap);      while(!tempmap.isempty()) {         iterator<entry<string, string>> iterator = tempmap.entryset().iterator();          while(iterator.hasnext()) {             entry<string, string> entry = iterator.next(); // !!!         }     }      return null; } 

to deep copy map use library: cloner

i marked line unfortunately ava.util.concurrentmodificationexception '!!!'

can please tell me why exception?

the complete code:

    cloner cloner = new cloner();      map<string, freebasetype> tempfreebasetypes = new hashmap<string, freebasetype>();     map<string, freebasetype> freebasetypescopy = cloner.deepclone(freebasetypes);      while(!freebasetypescopy.isempty()) {         iterator<entry<string, freebasetype>> iterator = freebasetypescopy.entryset().iterator();          while(iterator.hasnext()) {             entry<string, freebasetype> entry = iterator.next();              if(tempfreebasetypes.containskey(entry.getvalue().getsupertype()) || entry.getvalue().getsupertype() == null) {                 tempfreebasetypes.put(entry.getvalue().gettype(), entry.getvalue());                  freebasetypescopy.remove(entry.getkey());             }          }     }      list<freebasetype> sortedfreebasetypes = new arraylist<freebasetype>();     iterator<entry<string, freebasetype>> iterator = tempfreebasetypes.entryset().iterator();      while(iterator.hasnext()) {         entry<string, freebasetype> entry = iterator.next();          sortedfreebasetypes.add(entry.getvalue());     }      return sortedfreebasetypes; 

while iterate map iterator, not allowed modify map directly, or concurrentmodificationexception. way modify map indirectly through iterators remove() method, removes entry iterator pointing map.

replace line

freebasetypescopy.remove(entry.getkey()); 

with

iterator.remove(); 

and code should work.