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 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());
}
} |
Set created from Hashtable Keys contains : 3 2 1
Example 2:
// 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());
}
} |
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.