How to iterate over MultivaluedMap and extract the key and its corresponding first value?

Question

Here is my code its my first attempt . But what is the correct way to do this.

    private Map<String,String> prepareParameters(MultivaluedMap<String, String> queryParameters) {

    Map<String,String> parameters = new HashMap<String,String>();
    for (Map.Entry<String,List<String>> e : queryParameters.entrySet()) {
        parameters.put(e.getKey(), e.getValue().get(0));
    }

But the List is. The values of the keys in the Map are List of String. I may be wrong feel free to correct me. — John Doe, Jul 28 '14 at 08:29
But each time you'll get a different List as you don't know which is at place one. Making sense ? — Suresh Atta, Jul 28 '14 at 08:30
What I want is that this method should return a map of key and its corresponding first value. I know there is a method getFirst() in MultivaluedMap. How to use it here? — John Doe, Jul 28 '14 at 08:36

John Doe · Accepted Answer · 2017-09-19T16:52:08.877

One way to do this can be :--

  private Map<String,String> prepareParameters(MultivaluedMap<String, String> queryParameters) {

   Map<String,String> parameters = new HashMap<String,String>();

   Iterator<String> it = queryParameters.keySet().iterator();


         while(it.hasNext()){
           String theKey = (String)it.next();
           parameters.put(theKey,queryParameters.getFirst(theKey));
       }

   return parameters;

    }

OR without using the iterator, as suggested by Dinei Rockenbach, we can do as follow:-

  private Map<String,String> prepareParameters(MultivaluedMap<String, String> queryParameters) {

   Map<String,String> parameters = new HashMap<String,String>();

   for(String str : queryParameters.keySet()){
     parameters.put(str, queryParameters.getFirst(str));
   }
   return parameters;

    }

One could simply use `for(String theKey : queryParameters.keySet()) { ... }` instead of working directly with `Iterator`. — Dinei, Jun 23 '17 at 19:49

score 2 · Answer 2 · edited Nov 16 '21 at 09:27

2

Or using streams...

queryParameters.getRequestHeaders().entrySet().stream()
.collect(
    Collectors.toMap(
        Map.Entry::getKey, entry -> entry.getValue().stream().findFirst().orElse(null)));

edited Nov 16 '21 at 09:27

Jainendra

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answered Nov 16 '19 at 14:18

Gregor

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How to iterate over MultivaluedMap and extract the key and its corresponding first value?

2 Answers2