Concurrentmodificationexception problems in Java

1  Public Static voidHashseterror () {2map<string, set<string>> tempMap1 =NewHashmap<string, set<string>>();3          for(inti = 0; I < 10; i++) {4Set<string> set =NewHashset<string>();5 Set.add (string.valueof (i));6Set.add (String.valueof (i*10));7 Tempmap1.put (string.valueof (i), set);8         }9 Tenmap<string, set<string>> tempMap2 =NewHashmap<string, set<string>>(); One  Aset<string> set = Tempmap1.get (String.valueof (5)); -Tempmap2.put ("T", set); -          the          for(String str:set) { -set<string> Tempset = tempmap2.get ("T"); -Tempset.add (str+ "12");  -         } +  -}

Execute error

Analysis Reason:

Although there are no noticeable modifications and additions to the set, it has actually increased.

TempMap2 gets set<string> [5,50] from TempMap1, which points to TEMPMAP2 's key value reference to the Set<string> collection.

Therefore TempMap1 's key= "5" and TempMap2 's key= "T" point to the same set<string> set

When 17 rows change Tempmap2, the set set changes TempMap1 key= "5" of the value reference is constant but the object value has changed.

Workaround:

Tempmap2.put ("T", New Hashset<string> (set));
Using the keyword new to re-open a memory space, 2 references point to a different location, one change, and the other is unaffected.

Concurrentmodificationexception problems with Java