![]() ![]() (HashMap is roughly equivalent to Hashtable. ex : Map map new Hashmap () map.put ('key1','value1') map.You must use containsKey() method for checking the existence of a Key in HashMap not the get() method.It is because a return value of null does not necessarily indicate that the map contains no mapping for the key,its also possible that the map explicitly maps the key to null. This implementation provides all of the optional Map operations, and permits null values and the null key. A hashmap is a structure that is optimized for associative access of the values using the keys, but is in no way better in doing the reverse then an array for instance. To get keys in HashMap, We have keySet () method which is present in package. (The HashMap class is roughly equivalent to Hashtable, except that it is unsynchronized and permits nulls.) This class makes no guarantees as to the order of the map in particular, it does not guarantee that the order will remain constant. There is no iterator method in the HashMap, so directly it is. This implementation provides all of the optional map operations, and permits null values and the null key. Import java.util.* public class HashMapGetExample How to get keys and values from HashMap This is the most asked questions in the Java interviews. ![]()
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