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Hashtable containsKey() Method in Java
  • Last Updated : 28 Jun, 2018

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() method
import 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() method
import 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.

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