Java

Vector is synchronized, ArrayList is not synchronized
ArrayList is faster
Both grow and shrink dynamically, the increment of ArrayList is 50%, the increment of Vector is 100%
Both have Enumeration and Iterator
ArrayList is preferrable when there is no specific requirement

ArrayList is an implementation of dynamica array, LinkedList is a double linked list
Insertion is O(1) with LinkedList, O(n) in worst-case and O(1) in best-caset with ArrayList
Removal is O(1) with LinkedList, O(n) with ArrayList
LinkedList has more memory overhead
Accessing an element is O(n) with LinkedList, O(1) with ArrayList
Search is O(n) for both, but ArrayList is able to use binary search which is O(logn)

HashMap
- It is implemented by an array of linked lists
- 0(1) lookup and insertion
- A HashMap contains values based on the key
- It contains only unique elements
- It may have one null key and multiple null values
- It maintains no order
LinkedHashMap
- It is implemented by doubly-linked buckets
- 0(1) lookup and insertion
- A LinkedHashMap contains values based on the key
- It contains only unique elements
- It may have one null key and multiple null values
- It is same as HashMap instead maintains insertion order
TreeMap
- TreeMap is implemented by a Red-Black Tree
- O(log N) lookup and insertion
- A TreeMap contains values based on the key
- It contains only unique elements
- It cannot have null key but can have multiple null values
- It is same as HashMap instead maintains ascending order sorted using the natural order of its key
Hashtable
- A Hashtable is an array of list
- It contains only unique elements
- It may have not have any null key or value
- It is synchronized

HashMap is non synchronized. It is not-thread safe and can’t be shared between many threads without proper synchronization code whereas Hashtable is synchronized. It is thread-safe and can be shared with many threads
HashMap allows one null key and multiple null values whereas Hashtable doesn’t allow any null key or value
HashMap is generally preferred over HashTable if thread synchronization is not needed
HashMap is an advanced version and improvement on the Hashtable. HashMap was created later

In HashMap , entry object(entry object stores key-value pairs) is not eligible for garbage collection
In WeakHashmap, when a key is discarded then its entry is automatically removed from the map

It is not recommended to use remove() of list interface when iterating over elements. This may lead to ConcurrentModificationException (Refer this for a sample program with this exception). When iterating over elements, it is recommended to use Iterator.remove() method