Java how to convert HashMap String Object to array

Question

I need to convert a HashMap lt String  Object gt  to an array  could anyone show me how it s done

User · Answer

To Get in One Dimension Array        String   arr1   new String hashmap size         String   arr2   new String hashmap size         Set entries   hashmap entrySet        Iterator entriesIterator   entries iterator         int i   0      while entriesIterator hasNext              Map Entry mapping    Map Entry  entriesIterator next             arr1 i    mapping getKey   toString            arr2 i    mapping getValue   toString             i             To Get in two Dimension Array         String     arr   new String hashmap size    2      Set entries   hashmap entrySet       Iterator entriesIterator   entries iterator        int i   0     while entriesIterator hasNext          Map Entry mapping    Map Entry  entriesIterator next         arr i  0    mapping getKey   toString        arr i  1    mapping getValue   toString         i

User · Answer

hashMap keySet   toArray       returns an array of keys hashMap values   toArray       returns an array of values     Edit  It should be noted that the ordering of both arrays may not be the same  See oxbow lakes answer for a better approach for iteration when the pair key values are needed

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HashMap lt String  String gt  hashMap   new HashMap lt  gt     String   stringValues  new String hashMap values   size     hashMap values   toArray stringValues

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You may try this too   public static String     getArrayFromHash Hashtable lt String String gt  data           String     str   null                        Object   keys   data keySet   toArray                Object   values   data values   toArray                str   new String keys length  values length               for int i 0 i lt keys length i                      str 0  i     String keys i                   str 1  i     String values i                                   return str          Here I am using String as return type  You may change it to required return type by you

User · Answer

If you want the keys and values  you can always do this via the entrySet   hashMap entrySet   toArray       returns a Map Entry lt K V gt      From each entry you can  of course  get both the key and value via the getKey and getValue methods

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Map lt String  String gt  map   new HashMap lt String  String gt     map put  key1    value1    map put  key2    value2     Object     twoDarray   new Object map size    2    Object   keys   map keySet   toArray    Object   values   map values   toArray     for  int row   0  row  lt  twoDarray length  row          twoDarray row  0    keys row       twoDarray row  1    values row         Print out the new 2D array for  int i   0  i  lt  twoDarray length  i          for  int j   0  j  lt  twoDarray i  length  j              System out println twoDarray i  j

User · Answer

If you are using Java 8  and need a 2 dimensional Array  perhaps for TestNG data providers  you can try     map entrySet        stream        map e - gt  new Object   e getKey    e getValue          toArray Object      new     If your Objects are Strings and you need a String      try   map entrySet        stream        map e - gt  new String   e getKey    e getValue   toString          toArray String      new

User · Answer

SuppressWarnings  unchecked       public static  lt E T gt  E   hashMapKeysToArray HashMap lt E T gt  map                int s          if map    null     s   map size    lt 1              return null           E   temp          E typeHelper          try                       Iterator lt Entry lt E  T gt  gt  iterator   map entrySet   iterator                Entry lt E  T gt  iK   iterator next                typeHelper   iK getKey                 Object o   Array newInstance typeHelper getClass    s               temp    E    o               int index   0              for  Map Entry lt E T gt  mapEntry   map entrySet                                  temp index      mapEntry getKey                                    catch  Exception e                        return null                    return temp          --------------------------------------------------------      SuppressWarnings  unchecked       public static  lt E T gt  T   hashMapValuesToArray HashMap lt E T gt  map                int s          if map    null     s   map size    lt 1              return null           T   temp          T typeHelper          try                       Iterator lt Entry lt E  T gt  gt  iterator   map entrySet   iterator                Entry lt E  T gt  iK   iterator next                typeHelper   iK getValue                 Object o   Array newInstance typeHelper getClass    s               temp    T    o               int index   0              for  Map Entry lt E T gt  mapEntry   map entrySet                                  temp index      mapEntry getValue                                    catch  Exception e           return null            return temp

User · Answer

To guarantee the correct order for each array of Keys and Values  use this  the other answers use individual Sets which offer no guarantee as to order   Map lt String  Object gt  map   new HashMap lt String  Object gt     String   keys   new String map size     Object   values   new Object map size     int index   0  for  Map Entry lt String  Object gt  mapEntry   map entrySet          keys index    mapEntry getKey        values index    mapEntry getValue        index

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An alternative to CrackerJacks suggestion  if you want the HashMap to maintain order you could consider using a LinkedHashMap instead  As far as im aware it s functionality is identical to a HashMap but it is FIFO so it maintains the order in which items were added

User · Answer

I used almost the same as  kmccoy  but instead of a keySet   I did this  hashMap values   toArray new MyObject 0

User · Answer

If you have HashMap lt String  SomeObject gt  hashMap then   hashMap values   toArray      Will return an Object    If instead you want an array of the type SomeObject  you could use   hashMap values   toArray new SomeObject 0

[java] Java: how to convert HashMap<String, Object> to array

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