How to iterate over all keys in a Map?

There are various approaches to iterate over all keys in a Map:

1. Iteration over keySet():

   // Get a Set of all keys and iterate over it
   for (KeyType key : map.keySet()) {
       // Actions with the key
       // ValueType value = map.get(key); // You can get the value if needed
   }
   

2. Using Streams with keySet():

   // Get a stream of keys and process them
   map.keySet().stream().forEach(key -> {
       // Actions with the key
       // ValueType value = map.get(key); // You can get the value if needed
   });
   

3. Using lambda expressions with forEach (Java 8 and above),

   Although forEach is available for Map, it directly iterates over key-value pairs (Entry), not just keys. To get only keys, a different approach is needed.

4. Iteration using Iterator over keySet():

   // Get an iterator for the Set of keys
   Iterator<KeyType> iterator = map.keySet().iterator();
   while (iterator.hasNext()) {
       KeyType key = iterator.next();
       // Actions with the key
       // ValueType value = map.get(key); // You can get the value if needed
   }
   

The most common and readable methods are iterating over keySet() with an enhanced for loop or using streams. The choice depends on the specific task and preferences.