How to for each the hashmap

Question

I have this field   HashMap lt String  HashMap gt  selects   new HashMap lt String  HashMap gt       For each Hash lt String  HashMap gt  I need to create a ComboBox  whose items are the value  which happens to be a HashMap itself  of HashMap  lt String    HashMap   gt    By way of  non-functioning  demonstration   for  int i 0  i  lt  selects size    i          HashMap h   selects i  getValue        ComboBox cb   new ComboBox         for  int y 0  y  lt  h size    i              cb items add h y  getValue

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Streams Java 8  Along with forEach method that accepts a lambda expression we have also got stream APIs  in Java 8   Iterate over entries  Using forEach and Streams    sample forEach  k v  - gt  System out println k         v     sample entrySet   stream   forEachOrdered  entry  - gt                Object currentKey   entry getKey                Object currentValue   entry getValue                System out println currentKey         currentValue               sample entrySet   parallelStream   forEach  entry  - gt                Object currentKey   entry getKey                Object currentValue   entry getValue                System out println currentKey         currentValue                 The advantage with streams is they can be parallelized easily and can be useful when we have multiple CPUs at disposal  We simply need to use parallelStream   in place of stream   above  With parallel streams it makes more sense to use forEach as forEachOrdered would make no difference in performance  If we want to iterate over keys we can use sample keySet   and for values sample values     Why forEachOrdered and not forEach with streams    Streams also provide forEach method but the behaviour of forEach is explicitly nondeterministic where as the forEachOrdered performs an action for each element of this stream  in the encounter order of the stream if the stream has a defined encounter order  So forEach does not guarantee that the order would be kept  Also check this for more

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I generally do the same as cx42net  but I don t explicitly create an Entry   HashMap lt String  HashMap gt  selects   new HashMap lt String  HashMap gt     for  String key   selects keySet          HashMap lt innerKey  String gt  boxHolder   selects get key       ComboBox cb   new ComboBox        for  InnerKey innerKey   boxHolder keySet                  cb items add boxHolder get innerKey              This just seems the most intuitive to me  I think I m prejudiced against iterating over the values of a map

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Lambda Expression Java 8   In Java 1 8  Java 8  this has become lot easier by using forEach method from Aggregate operations Stream operations  that looks similar to iterators from Iterable Interface    Just copy paste below statement to your code and rename the HashMap variable from hm to your HashMap variable to print out key-value pair   HashMap lt Integer Integer gt  hm   new HashMap lt Integer  Integer gt               Logic to put the Key Value pair in your HashMap hm         Print the key value pair in one line  hm forEach  k v  - gt  System out println  key    k   value   v      Here is an example where a Lambda Expression is used       HashMap lt Integer Integer gt  hm   new HashMap lt Integer  Integer gt         Random rand   new Random 47       int i 0      while i lt 5           i            int key   rand nextInt 20           int value   rand nextInt 50           System out println  Inserting key    key   Value    value           Integer imap  hm put key value           if  imap    null               System out println  Inserted                      else              System out println  Replaced with   imap                                       hm forEach  k v  - gt  System out println  key    k   value   v     Output   Inserting key  18 Value  5 Inserted Inserting key  13 Value  11 Inserted Inserting key  1 Value  29 Inserted Inserting key  8 Value  0 Inserted Inserting key  2 Value  7 Inserted key  1 value 29 key  18 value 5 key  2 value 7 key  8 value 0 key  13 value 11   Also one can use Spliterator for the same   Spliterator sit   hm entrySet   spliterator      UPDATE    Including documentation links to Oracle Docs  For more on Lambda go to this link and must read Aggregate Operations and for Spliterator go to this link

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Map values     HashMap lt String  HashMap lt SomeInnerKeyType  String gt  gt  selects       new HashMap lt String  HashMap lt SomeInnerKeyType  String gt  gt           for HashMap lt SomeInnerKeyType  String gt  h   selects values         ComboBox cb   new ComboBox       for String s   h values               cb items add s

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I know I m a bit late for that one  but I ll share what I did too  in case it helps someone else    HashMap lt String  HashMap gt  selects   new HashMap lt String  HashMap gt      for Map Entry lt String  HashMap gt  entry   selects entrySet          String key   entry getKey        HashMap value   entry getValue            do what you have to do here        In your case  another loop

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Use entrySet          Output   D  99 22 A  3434 34 C  1378 0 B  123 22 E  -19 08  B s new balance  1123 22      import java util HashMap  import java util Map  import java util Set   public class MainClass     public static void main String args           HashMap lt String  Double gt  hm   new HashMap lt String  Double gt          hm put  A   new Double 3434 34        hm put  B   new Double 123 22        hm put  C   new Double 1378 00        hm put  D   new Double 99 22        hm put  E   new Double -19 08         Set lt Map Entry lt String  Double gt  gt  set   hm entrySet         for  Map Entry lt String  Double gt  me   set          System out print me getKey                  System out println me getValue                System out println         double balance   hm get  B        hm put  B   balance   1000        System out println  B s new balance      hm get  B             see complete example here    http   www java2s com Code JavaAPI java util HashMapentrySet htm

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You can iterate over a HashMap  and many other collections  using an iterator  e g    HashMap lt T U gt  map   new HashMap lt T U gt           Iterator it   map values   iterator     while  it hasNext          System out println it next

[java] How to for each the hashmap?

Streams Java 8

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