How to Serialize a collection in java? How to serialize a ArrayList, Hashmap or Hashset object in Java

All standard implementations of collections List, Set and Map interface already implement java.io.Serializable. All the commonly used collection classes like java.util.ArrayList, java.util.Vector, java.util.Hashmap, java.util.Hashtable, java.util.HashSet, java.util.TreeSet do implement Serializable. This means you do not really need to write anything specific to serialize collection objects. However you should keep following things in mind before you serialize a collection object – Make sure all the objects added in collection are Serializable. – Serializing the collection can be costly therefore make sure you serialize only required data isntead of serializing the whole collection. – In case you are using a custom implementation of Collection interface then you may need to implement serialization for it.