Java Utility Library

Java Hashtable - replace() Method

The java.util.Hashtable.replace() method is used to replace the entry for the specified key only if it is currently mapped to the specified value.

Syntax

public boolean replace(K key, V oldValue, V newValue)

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

Parameters

`key`	Specify the key with which the specified value is associated.
`oldValue`	Specify value expected to be associated with the specified key.
`newValue`	Specify value to be associated with the specified key.

Return Value

Returns true if the value was replaced.

Exception

NA.

Example:

In the example below, the java.util.Hashtable.replace() method is used to replace the entry for the specified key in the given hashtable.

import java.util.*;

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

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

    //printing hashtable
    System.out.println("Before replace, Htable contains: " + Htable);    

    //replacing the value associated with 101 key
    Htable.replace(101, "John", "Sam");
    //replacing the value associated with 102 key
    //it is not replaced as oldValue is not matching
    Htable.replace(102, "Jo", "Peter");     

    //printing hashtable
    System.out.println("After replace, Htable contains: " + Htable);  
  }
}

The output of the above code will be:

Before replace, Htable contains: {103=Kim, 102=Marry, 101=John}
After replace, Htable contains: {103=Kim, 102=Marry, 101=Sam}

❮ Java.util - Hashtable