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Java Hashtable put() Method with Example

Hashtable Class put() method: Here, we are going to learn about the put() method of Hashtable Class with its syntax and example.
Submitted by Preeti Jain, on February 17, 2020

Hashtable Class put() method

  • put() method is available in java.util package.
  • put() method is used to put the given key element (key_ele) to the given value element (val_ele).
  • put() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.
  • put() method may throw an exception at the time of put key-value pairs.
    NullPointerException: This exception may throw when any of the given parameters is null exists.


    public Value put(Key key_ele , Value val_ele);


  • Key key_ele – represent the key element (key_ele) in this Hashtable.
  • Value val_ele – represent the value element (val_ele) in this Hashtable.

Return value:

The return type of the method is Value, it returns old value linked with the given key element (key_ele) when exists otherwise it returns null.


// Java program to demonstrate the example 
// of Value put(Key key_ele , Value val_ele)
// method of Hashtable 

import java.util.*;

public class PutOfHashtable {
    public static void main(String[] args) {

        //Instantiate a hashtable object  
        Hashtable ht = new Hashtable();

        // By using put() method is to
        // add the linked values in an
        // Hashtable ht
        ht.put(10, "C");
        ht.put(20, "C++");
        ht.put(30, "JAVA");
        ht.put(40, "PHP");
        ht.put(50, "SFDC");

        // Display Hashtable
        System.out.println("Hashtable :" + ht);

        // By using put() method is to replace
        // the value element exists on the key
        // element in this Hashtable
        ht.put(30, "Microservices");

        // Display Modified Hashtable
        System.out.println("ht.put(30,Microservices) :" + ht);


Hashtable :{10=C, 20=C++, 30=JAVA, 40=PHP, 50=SFDC}
ht.put(30,Microservices) :{10=C, 20=C++, 30=Microservices, 40=PHP, 50=SFDC}


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