how to copy one hashmap content to another hashmap

Question

Here I have two hashmaps dataz and screen_dataz. I want to copy screen_dataz to dataz.

I am trying like this but it's not working:

Object[]  obj = new Object[5];
String[] strArray = new String[]{"Obj1","Array1","Converted1","To1","List1"};
String[] strArray1 = new String[]{"Obj2","Array2","Converted2","To2","List2"};
dataz.put(0,(Object[]) strArray);
dataz.put(1,(Object[]) strArray1);
// String dataString = (String) dataz;
System.out.println(dataz);


Object[]  obj1= new Object[5];
String[] strArray2 = new String[]{"Obj3","Array3","Converted3","To3","List3"};
String[] strArray3 = new String[]{"Obj4","Array4","Converted4","To4","List4"};
screen_dataz.put(0,(Object[]) strArray2);
screen_dataz.put(1,(Object[]) strArray3);
System.out.println("copying screen dataz to dataz");
dataz.putAll(screen_dataz);

Please show the definition of `dataz` and `screen_dataz` and explain what you mean by "it's not working". — Duncan Jones, Jun 27 '13 at 07:44
Right, Until we have definition of `dataz`, a couple of answers below are arguably wrong !!! — Mukul Goel, Jun 27 '13 at 07:55

score 17 · Answer 1 · answered Jun 27 '13 at 07:46

17

Make use of constructor and Shallow it .

dataz = new HashMap<Key,val>(screen_dataz);

answered Jun 27 '13 at 07:46

Suresh Atta

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This *might* be a solution. But perhaps `dataz` already has some useful data in it. Probably worth waiting until the OP defines the question more closely. – Duncan Jones Jun 27 '13 at 07:48
1

hey, do `screen_dataz` and `dataz` refer to the same location? As I tried this and deleting values in `dataz` also deleted values from `screen_dataz`. I actually want to copy values from one map to a new map and not two variables referring to the same location. – Ram Patra Apr 09 '15 at 14:56

Maroun · Answer 2 · 2017-11-13T11:09:40.273

8

You can simply construct a new one:

dataz = new HashMap<Integer,Object>(screen_dataz);

edited Nov 13 '17 at 11:09

answered Jun 27 '13 at 07:46

Maroun

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beat you by 6 sec :) +1 :) – Suresh Atta Jun 27 '13 at 07:46
4

@Baadshah I'll take my revenge someday! Muahaha – Maroun Jun 27 '13 at 07:47
As far as I can tell, you've both rushed in with something that might be correct. But you've made a big assumption that `dataz` can be overwritten. – Duncan Jones Jun 27 '13 at 07:49
1

The term *Copying* made me to post that.Let see if its addingnew or not :) – Suresh Atta Jun 27 '13 at 07:53
1

@DuncanJones The same reason made me post the answer too :) However, you might be right.. – Maroun Jun 27 '13 at 08:04

score 6 · Answer 3 · edited May 23 '17 at 11:46

6

Map tmp = new HashMap(patch);
tmp.keySet().removeAll(target.keySet());
target.putAll(tmp);

For detailed explanation

edited May 23 '17 at 11:46

Community

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answered Jun 27 '13 at 07:45

Naveen Kumar Alone

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score 3 · Answer 4 · edited May 23 '17 at 11:46

3

It's already posted here

Map tmp = new HashMap(patch);
tmp.keySet().removeAll(target.keySet());
target.putAll(tmp);

edited May 23 '17 at 11:46

Community

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answered Jun 27 '13 at 07:45

u.jegan

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score 2 · Accepted Answer · answered Jun 27 '13 at 07:46

Looks like it's not working because you're using the same keys (0 and 1) both in dataz and in screen_dataz.

According to the official javadoc, putAll "will replace any mappings that this map had for any of the keys currently in the specified map.", so you are now losing your previous objects contained in dataz.

score 1 · Answer 6 · answered Jun 27 '13 at 07:56

1

Try this

    HashMap<Integer,String> myMap=new HashMap<>();
    myMap.put(1,"A");
    myMap.put(2,"B");
    HashMap<Integer,String> newMap=new HashMap<>();
    newMap.putAll(myMap);

answered Jun 27 '13 at 07:56

Ruchira Gayan Ranaweera

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score 0 · Answer 7 · answered Jun 27 '13 at 07:55

0

HashMap<String, String> hash1 = new HashMap();
    hash1.put("one", "the firs one");
    hash1.put("two", "the second one");
    hash1.put("three", "the third one");
    HashMap<String, String> hash2 = new HashMap<>();
    hash2.putAll(hash1);

answered Jun 27 '13 at 07:55

Mostafa Jamareh

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how to copy one hashmap content to another hashmap

7 Answers7