1. Collection vs Collections
First of all, “Collection” and “Collections” are two different concepts. As you will see from the hierarchy diagram below, “Collection” is a root interface in the Collection hierarchy but “Collections” is a class which provide static methods to manipulate on some Collection types.
2. Class hierarchy of Collection
The following diagram demonstrates class hierarchy of Collection.
3. Class hierarchy of Map
Here is class hierarchy of Map.
4. Summary of classes
5. Code Example
The following is a simple example to illustrate some collection types:
List<String> a1 = new ArrayList<String>(); a1.add("Program"); a1.add("Creek"); a1.add("Java"); a1.add("Java"); System.out.println("ArrayList Elements"); System.out.print("\t" + a1 + "\n"); List<String> l1 = new LinkedList<String>(); l1.add("Program"); l1.add("Creek"); l1.add("Java"); l1.add("Java"); System.out.println("LinkedList Elements"); System.out.print("\t" + l1 + "\n"); Set<String> s1 = new HashSet<String>(); // or new TreeSet() will order the elements; s1.add("Program"); s1.add("Creek"); s1.add("Java"); s1.add("Java"); s1.add("tutorial"); System.out.println("Set Elements"); System.out.print("\t" + s1 + "\n"); Map<String, String> m1 = new HashMap<String, String>(); // or new TreeMap() will order based on keys m1.put("Windows", "2000"); m1.put("Windows", "XP"); m1.put("Language", "Java"); m1.put("Website", "programcreek.com"); System.out.println("Map Elements"); System.out.print("\t" + m1); |
Output:
ArrayList Elements
[Program, Creek, Java, Java]
LinkedList Elements
[Program, Creek, Java, Java]
Set Elements
[tutorial, Creek, Program, Java]
Map Elements
{Windows=XP, Website=programcreek.com, Language=Java}
this is very helpful blog about java
It is help full
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If I wanna add BST to the collection. where should it come?
u missed the abstractinterface,such as abstractcollection,abstractset,abstractlist,Those are important in the hierarchy of java collection.
It is very crisp and clear..
great explanation… very useful….
The graph is very clear~
You forget
interface NavigableMap
Clear explanation, great work!
Very good explanation with clear diagrams. Thanks.
Excellent illustration. Thanks a lot.
it is helpful