Hashtable keySet() Method in Java with Examples

Last Updated : 15 Oct, 2020

The java.util.Hashtable is used to create a set of key elements in the hash table. It basically returns a set view of the keys, or we can create a new set and store the key elements in them.

Syntax:

public Set<K> keySet()

K : type of the Keys in the hash table

Parameters: The method does not take any parameter.

Return Value: The method returns a set having the keys of the hash table.

Below programs are used to illustrate the working of java.util.Hashtable.keySet() Method:
Example 1:

Java

// Java code to illustrate the keySet() method // to get Set view of Keys from a Hashtable.  import java.util.Enumeration; import java.util.Iterator; import java.util.Hashtable; import java.util.Set;  public class Example1 {      public static void main(String[] args)     {          // Creating an empty Hashtable         Hashtable<String, String> hash_t             = new Hashtable<String, String>();          // Add mappings into the table         hash_t.put("1", "Geeks");         hash_t.put("2", "For");         hash_t.put("3", "Geeks");          // Getting a Set of keys using         // keySet() method of Hashtable class         Set hash_set = hash_t.keySet();          System.out.println(             "Set created from Hashtable Keys contains :");          // Iterating through the Set of keys         Iterator itr = hash_set.iterator();         while (itr.hasNext())             System.out.println(itr.next());     } }

Output

Set created from Hashtable Keys contains :  3  2  1

Example 2:

Java

// Java code to illustrate the keySet() method // to get Set view of Keys from a Hashtable.  import java.util.Enumeration; import java.util.Iterator; import java.util.Hashtable; import java.util.Set;  public class Example2 {      public static void main(String[] args)     {          // Creating an empty Hashtable         Hashtable<String, String> hash_t             = new Hashtable<String, String>();          // Inserting elements into the table         hash_t.put("Geeks", "1");         hash_t.put("For", "2");         hash_t.put("geeks", "3");          // Getting a Set of keys using         // keySet() method of Hashtable class         Set hash_set = hash_t.keySet();          System.out.println(             "Set created from Hashtable Keys contains :");          // Iterating through the Set of keys         Iterator itr = hash_set.iterator();         while (itr.hasNext())             System.out.println(itr.next());     } }

Output

Set created from Hashtable Keys contains :  For  Geeks  geeks

Note: The same operation can be performed with any type of Mappings with variation and combination of different data types.

Hashtable keySet() Method in Java with Examples

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Hashtable keySet() Method in Java with Examples

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