java - how to do deep copy of hashmap

Asked Sep 30 '15 at 13:29

Active Sep 30 '15 at 13:37

Viewed 126 times

How to deep copy hashmap? I wanna make a copy of hashmap. When I change the keys and values in the copy, the original hashmap doesn't change. I cannot find a solution to solve this problem in the Internet. The function of putall() doesn't work.

HashMap<OWLClass, Set<OWLClass>> map1 ;
HashMap<OWLClass, Set<OWLClass>> map2 = new HashMap<OWLClass, Set<OWLClass>>();

I tried

for(OWLClass map1.keySet()){
        map2.put(a, map1.get(a));
    }

and

map2.putAll(map1);

Both these methonds don't work.

edited Sep 30 '15 at 13:37

asked Sep 30 '15 at 13:29

dakongyi

Possible duplicate of [Java HashMap - deep copy](http://stackoverflow.com/questions/13049222/java-hashmap-deep-copy) – Zeeshan Sep 30 '15 at 13:32
*When I change the keys and values in the copy, the original hashmap doesn't change.* Well, that's good, right? – Manu Sep 30 '15 at 13:32
You need one more step `for(OWLClass map1.keySet()){ map2.put(a, new HashSet<>(map1.get(a))); }` – Peter Lawrey Sep 30 '15 at 13:49
@PeterLawrey Thank you so much!!! – dakongyi Sep 30 '15 at 15:16

java - how to do deep copy of hashmap

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