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.
