Collection

General-purpose Implementations

Interfaces	Implementations
	Hash table	Resizable array	Tree	Linked list	Hash table + Linked list
Set	HashSet		TreeSet		LinkedHashSet
List		ArrayList		LinkedList
Queue
Map	HashMap		TreeMap		LinkedHashMap

A Set and a Map cannot contain duplicates A Map contains pairs of (key;object). the elements are ordered and can be accessed by the key

SAX V/S DOM

Instead of reading a document one piece at a time (as with SAX), a DOM parser reads an entire document. It then makes the tree for the entire document available to program code for reading and updating. Simply put, the difference between SAX and DOM is the difference between sequential, read-only access, and random, read-write access.

When to use DOM

---

If your XML documents contain document data (e.g., Framemaker documents stored in XML format), then DOM is a completely natural fit for your solution. If you are creating some sort of document information management system, then you will probably have to deal with a lot of document data. An example of this is the Datachannel RIO product, which can index and organize information that comes from all kinds of document sources (like Word and Excel files). In this case, DOM is well suited to allow programs access to information stored in these documents.

However, if you are dealing mostly with structured data (the equivalent of serialized Java objects in XML) DOM is not the best choice. That is when SAX might be a better fit.

When to use SAX

---

If the information stored in your XML documents is machine readable (and generated) data then SAX is the right API for giving your programs access to this information. Machine readable and generated data include things like:

• Java object properties stored in XML format
• queries that are formulated using some kind of text based query language (SQL, XQL, OQL)
• result sets that are generated based on queries (this might include data in relational database tables encoded into XML).