Java Collections - Array, ArrayList, HashTable

Array vs ArrayList in Java:
Array - Fixed Size, Same Data Types only

1. int[] myArr = new int[10];
2. myArr[0] = 10;
3. System.out.println( myArr[0] );
4. System.out.println( myArr.length );

ArrayList - Dynamic Size, Different data types but not primitive types, Synchronized.

1. ArrayList<String> myList = new ArrayList<String>();
2. myList.add("abcd");
3. myList.add(10);   //Adds in end of list because index not mentioned.
4. System.out.println( myList.get(0) );
   
   
   //Lot of methods are there here.
5. add(index, Value);
6. addAll(collection);
7. clear()
8. contains(value)
9. indexOf(value)
10. get(index)
11. isEmpty()
12. lastIndexOf(value)
13. set(index, value) //Replace the value
14. size()
15. toArray()
16. iterator()   // One-Directional, only access
17. listIterator() //Bi-Dierectional, allows modification

HashTable vs HashMap vs HashSet:
HashTable - Syncronized, will not allow NULL key/value.
- put, get
HashMap - UnSyncronized, will allow NULL key/value (so maybe good performance than HashTable)
- put, get
HashSet - Will allow duplicate values
- add, contains, get