Java Hashtable - put() Method

The java.util.Hashtable.put() method is used to map the specified key to the specified value in the hashtable. Please note that neither the key nor the value can be null. If the key is already present in the map, the old value is replaced.

Syntax

public V put(K key, V value)

Here, K and V are the type of key and value respectively maintained by the container.

Parameters

Return Value

Returns previous value associated with given key, or null if it did not have one.

Exception

NA

Example:

In the example below, the java.util.Hashtable.put() method is used to map the specified key to the specified value in the given hashtable.

import java.util.*;

public class MyClass {
  public static void main(String[] args) {
    //creating a hashtable
    Hashtable<Integer, String> Htable = new Hashtable<Integer, String>();

    //populating hashtable
    Htable.put(101, "John");
    Htable.put(102, "Marry");
    Htable.put(103, "Kim");
    Htable.put(104, "Jo");

    //printing hash map
    System.out.println("Htable contains: " + Htable);    

    //change a key-value pair
    Htable.put(103, "Ramesh"); 

    //printing hash map
    System.out.println("Htable contains: " + Htable);  
  }
}

The output of the above code will be:

Htable contains: {104=Jo, 103=Kim, 102=Marry, 101=John}
Htable contains: {104=Jo, 103=Ramesh, 102=Marry, 101=John}