Description
Program to get the Set of keys from HashMap.
Example
import java.util.Iterator;
import java.util.HashMap;
import java.util.Set;
class HashMapExample{
public static void main(String args[]) {
// Create a HashMap
HashMap<String, String> hmap = new HashMap<String, String>();
// Adding few elements
hmap.put("Key1", "Jack");
hmap.put("Key2", "Rock");
hmap.put("Key3", "Rick");
hmap.put("Key4", "Smith");
hmap.put("Key5", "Will");
// Getting Set of HashMap keys
/* public Set<K> keySet(): Returns a Set view of the keys contained
* in this map. The set is backed by the map, so changes to the map
* are reflected in the set, and vice-versa.
*/
Set<String> keys = hmap.keySet();
System.out.println("Set of Keys contains: ");
/* If your HashMap has integer keys then specify the iterator like
* this: Iterator<Integer> it = keys.iterator();
*/
Iterator<String> it = keys.iterator();
// Displaying keys. Output will not be in any particular order
while(it.hasNext()){
System.out.println(it.next());
}
}
}
Output:
Set of Keys contains: Key2 Key1 Key4 Key3 Key5
Note: The set of keys is backed up by original HashMap so if you remove any key from the Set it would automatically be removed from the HashMap.