The java.util.Hashtable.containsKey() method is used to check whether a particular key is present in the Hashtable or not. It takes the key element as a parameter and returns True if that element is present in the table.
Syntax:
Hash_table.containsKey(key_element)
Parameters: The method takes just one parameter key_element which refers to the key whose presence is supposed to be checked inside a Hashtable.
Return Value: The method returns boolean true if the key is present in the Hashtable otherwise it returns false.
Below programs are used to illustrate the working of java.util.Hashtable.containsKey() Method:
Program 1:
// Java code to illustrate the containsKey() methodimport java.util.*;  public class Hash_Table_Demo {    public static void main(String[] args)    {          // Creating an empty Hashtable        Hashtable<Integer, String> hash_table =         new Hashtable<Integer, String>();          // Putting values into the table        hash_table.put(10, "Geeks");        hash_table.put(15, "4");        hash_table.put(20, "Geeks");        hash_table.put(25, "Welcomes");        hash_table.put(30, "You");          // Displaying the Hashtable        System.out.println("Initial Table is: " + hash_table);          // Checking for the key_element '20'        System.out.println("Is the key '20' present? " +         hash_table.containsKey(20));          // Checking for the key_element '5'        System.out.println("Is the key '5' present? " +         hash_table.containsKey(5));    }} |
Output:
Initial Table is: {10=Geeks, 20=Geeks, 30=You, 15=4, 25=Welcomes}
Is the key '20' present? true
Is the key '5' present? false
Program 2:
// Java code to illustrate the containsKey() methodimport java.util.*;  public class Hash_Table_Demo {    public static void main(String[] args)    {          // Creating an empty Hashtable        Hashtable<String, Integer> hash_table=         new Hashtable<String, Integer>();          // Putting values into the table        hash_table.put("Geeks", 10);        hash_table.put("4", 15);        hash_table.put("Geeks", 20);        hash_table.put("Welcomes", 25);        hash_table.put("You", 30);          // Displaying the Hashtable        System.out.println("Initial Table is: " + hash_table);          // Checking for the key_element 'Welcomes'        System.out.println("Is the key 'Welcomes' present? " +         hash_table.containsKey("Welcomes"));          // Checking for the key_element 'World'        System.out.println("Is the key 'World' present? " +         hash_table.containsKey("World"));    }} |
Output:
Initial Table is: {You=30, Welcomes=25, 4=15, Geeks=20}
Is the key 'Welcomes' present? true
Is the key 'World' present? false
Note: The same operation can be performed with any type of variation and combination of different data types.
