title: Hashmap contains key value
body: <p>I want to get <code>containsKey</code> value in hashmap:</p>
  
  <pre><code>HashMap hm = new HashMap();
  for (Contact ru : registered_users) {
      hm.put(ru.getPhone(), ru.getId());
  }
  
  if(hm.containsKey(c.getPhone())) {
      registered_phone_contacts.add(new Contact("", c.getName());
                                                ^^
      // Here I need to get value.
  }
  </code></pre>
  
  <p>How can I do that?</p>