How to return a list of keys from a Hash Map

Question

I m currently trying to make a program that conjugates verbs into Spanish   I ve created a Hash Table that contains a key and an instantiation of the object Verb   The key is a string that has the infinitive form of the verb  for example   hablar     This is the code that I have so far for the hash map   public class VerbHashMap        HashMap lt String  Verb gt  verbHashMap       public VerbHashMap            verbHashMap   new HashMap                 Each verb s key in the HashMap is based on the infinitive form of the verb   For example  the string  hablar  is the key for a Spanish verb   The class Verb has a method called getInfinitive   which returns a string that contains the infinitive form of the verb   public boolean addVerb Verb verb       if verbHashMap containsValue verb getInfinitive             return false            else          verbHashMap put verb getInfinitive    verb           return true            The question is what is the most efficient way to create a method that returns a list of all the verbs in the Hash Map in alphabetical order   Should I have the method return an ArrayList which includes the keys of all the objects in the Hash Map   Or is there a much more efficient way to go about this

User · Accepted Answer

Use the keySet   method to return a set with all the keys of a Map   If you want to keep your Map ordered you can use a TreeMap

User · Answer

for int i 0 i lt ytFiles size   i                          int key   ytFiles keyAt i                       Log e  key   String valueOf key                        String format   ytFiles get key  getFormat   toString                        String url   ytFiles get key  getUrl                        Log e  url  url                       you can get key by method keyat and you have to pass the index then it will return key at that particular index  this loop will get all the key

User · Answer

map keySet     will return you all the keys  If you want the keys to be sorted  you might consider a TreeMap

User · Answer

Using map keySet    you can get a set of keys  Then convert this set into List by   List lt String gt  l   new ArrayList lt String gt  map keySet       And then use l get int  method to access keys   PS - source- Most concise way to convert a Set lt String gt  to a List lt String gt

User · Answer

List lt String gt  yourList   new ArrayList lt  gt  map keySet       This is will do just fine

User · Answer

Since Java 8   List lt String gt  myList   map keySet   stream   collect Collectors toList

[java] How to return a list of keys from a Hash Map?

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