Hashtable contains() Method in Java

28 Jun, 2018
The java.util.Hashtable.contains(Object value) method in Java is used to check whether a particular value is being mapped by any keys present in the Hashtable.
Syntax:
Hash_table.contains(Object value)
Parameters: The method accepts one parameter value of object type and refers to the value of the hashtable whose mapping is to be verified.
Return Value: The method returns a boolean true value if the passed value is mapped by any of the keys in the Hashtable.
Exceptions: The method throws NullPointerException if the passed value is Null.
Below programs illustrate the working of the above-mentioned method:Program 1:
// Java code to illustrate the contains() 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>();          // Mapping string values to int keys        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 HashMap        System.out.println("Initial Table is: " + hash_table);          // Checking for the Value 'Geeks'        System.out.println("Is the value 'Geeks' present? " +         hash_table.contains("Geeks"));          // Checking for the Value 'World'        System.out.println("Is the value 'World' present? " +         hash_table.contains("World"));    }}
Initial Table is: {10=Geeks, 20=Geeks, 30=You, 15=4, 25=Welcomes}
Is the value 'Geeks' present? true
Is the value 'World' present? false

Program 2:
// Java code to illustrate the contains() 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>();          // Mapping int values to string keys        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 Mappings are: " + hash_table);          // Checking for the Value '10'        System.out.println("Is the value '10' present? " +         hash_table.containsValue(10));          // Checking for the Value '30'        System.out.println("Is the value '30' present? " +         hash_table.containsValue(30));          // Checking for the Value '40'        System.out.println("Is the value '40' present? " +         hash_table.containsValue(40));    }}
Initial Mappings are: {You=30, Welcomes=25, 4=15, Geeks=20}
Is the value '10' present? false
Is the value '30' present? true
Is the value '40' present? false

Java - util package
Java-Collections
Java-HashTable
Java
Java
Java-Collections
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