Example of the putAll() method of Hashtable in Java

This tutorial shows how to copy all key-value pairs from one Hashtable to another in Java using the java.util.Hashtable.putAll().

public void putAll(Map t): This method is used to copy all elements from the Map specified to Hashtable. It throws an exception nullPointerException if the Map object is null.

import java.util.Enumeration; 
import java.util.Hashtable; 

public class putAll_hashtable {
 public static void main(String[] s) {
 Hashtable table = new Hashtable(); 
 table.put("1", "val1"); 
 table.put("2", "val2"); 
 table.put("3", "val3"); 

 Hashtable table2 = new Hashtable(); 
 table2.put("4", "val4"); 
 table2.put("5", "val5"); 
 table2.put("6", "val6"); 

 table2.putAll(table); 
 
 Enumeration e = table2.keys(); 
 while (e.hasMoreElements()) {
 String key = (String) e.nextElement(); 
 System.out.println(key + " : " + table2.get(key)); 
 }
 }
}

Let's see what it looks like compiling and executing this code:

6 : val6
5 : val5
4 : val4
3 : val3
2 :  val2
1: val1

References:
Tutorials Point:  java.util.Hashtable.putAll() Method