Hashtable

• Hashtable is collection that stores elements in the form of key-value pairs.

• If key provided later its corresponding value can be easily retrieved from the Hashtable .

• Duplicate keys are not allowed but values can be duplicated

• Insertion order is not preserved and it is based on hashcode of the keys.

• Heterogeneous objects are  allowed  for key and value

• Null key or null value is not allowed .otherwise we will get NullPointerException.  

• It is not Synchronized.but we can synchronized by using method of collection class

                   public staic Map synchronizedMap(Map m);

Constructors:

• Hashtable m=new Hashtable();//creates an empty Hashtable object with default  initial capacity 11 and default fill ratio 0.75 .fill ratio is also known as Load Faction

• Hashtable m=new Hashtable(Map m); 

• Hashtable m=new Hashtable(int initialcapacity); 

• Hashtable m=new Hashtable(int initialcapacity float fillratio);