import java.util.Collection; import java.util.Enumeration; import java.util.Hashtable; import java.util.Set; public class HashtableDemo { public static void main(String args[]) { // Creating Hashtable for example Hashtable companies = new Hashtable(); // Java Hashtable example to put object into Hashtable // put(key, value) is used to insert object into map companies.put("Google", "United States"); companies.put("Nokia", "Finland"); companies.put("Sony", "Japan"); // Java Hashtable example to get Object from Hashtable // get(key) method is used to retrieve Objects from Hashtable companies.get("Google"); // Hashtable containsKey Example // Use containsKey(Object) method to check if an Object exits as key in // hashtable System.out.println("Does hashtable contains Google as key: " + companies.containsKey("Google")); // Hashtable containsValue Example // just like containsKey(), containsValue returns true if hashtable // contains specified object as value System.out.println("Does hashtable contains Japan as value: " + companies.containsValue("Japan")); // Hashtable enumeration Example // hashtabl.elements() return enumeration of all hashtable values Enumeration enumeration = companies.elements(); while (enumeration.hasMoreElements()) { System.out .println("hashtable values: " + enumeration.nextElement()); } // How to check if Hashtable is empty in Java // use isEmpty method of hashtable to check emptiness of hashtable in // Java System.out.println("Is companies hashtable empty: " + companies.isEmpty()); // How to find size of Hashtable in Java // use hashtable.size() method to find size of hashtable in Java System.out.println("Size of hashtable in Java: " + companies.size()); // How to get all values form hashtable in Java // you can use keySet() method to get a Set of all the keys of hashtable // in Java Set hashtableKeys = companies.keySet(); // you can also get enumeration of all keys by using method keys() Enumeration hashtableKeysEnum = companies.keys(); // How to get all keys from hashtable in Java // There are two ways to get all values form hashtalbe first by using // Enumeration and second getting values ad Collection Enumeration hashtableValuesEnum = companies.elements(); Collection hashtableValues = companies.values(); // Hashtable clear example // by using clear() we can reuse an existing hashtable, it clears all // mappings. companies.clear(); } } Output: Does hashtable contains Google as key: true Does hashtable contains Japan as value: true hashtable values: Finland hashtable values: United States hashtable values: Japan Is companies hashtable empty: false Size of hashtable in Java: 3