Collection framework
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The Collection Framework consists of three main parts: interfaces that define abstract data types, implementations of those interfaces, and algorithms that can operate on the interfaces and implementations. It includes core interfaces like Collection, List, Set, and Map as well as specialized interfaces like SortedSet and SortedMap. Implementations like ArrayList, LinkedList, HashSet, TreeSet, HashMap and TreeMap provide concrete versions of the interfaces. The Collections and Arrays classes contain predefined algorithms that support the framework.
![Collection Framework - I
An example that converts a Queue to a List
import java.util.*;
public class MainClass {
public static void main(String[] args) {
Queue queue = new LinkedList();
queue.add("Hello");
queue.add("World");
List list = new ArrayList(queue);
System.out.println(list);
} // output :: [Hello, World]
} 8](https://image.slidesharecdn.com/collectionframework-140914211155-phpapp01/85/Collection-framework-8-320.jpg)
![Collection Framework - I
This example converts a List to a Set.
import java.util.*;
public class MainClass {
public static void main(String[] args) {
List myList = new ArrayList();
myList.add("Hello");
myList.add("World");
myList.add("World");
Set set = new HashSet(myList);
System.out.println(set);
}
}
9](https://image.slidesharecdn.com/collectionframework-140914211155-phpapp01/85/Collection-framework-9-320.jpg)
Collection framework
- 1. Collection Framework - I consists of THREE parts • interfaces, the abstract data types that the framework supports. • implementations, the concrete versions of these interfaces. • algorithms, the predefined actions that can be defined on either the interfaces or their implementations. 1
- 2. Collection Framework - I • All implementations are unsynchronized. • All implementations are serializable and cloneable. • All implementations support having null elements. 2
- 3. Collection Framework - I • The predefined algorithms for supporting the framework are found in the Collections and Arrays classes. 3
- 4. Collection Framework - I • Framework - Four core interfaces • Two specializations for sorting 1. Collection 2. List 3. Set 4. Map 5. SortedSet 6. SortedMap 4
- 5. Collection Framework - I Interface type and its implementation 5 Interface Implemented Set HashSet, LinkedHashSet, EnumSet SortedSet TreeSet List Vector, Stack, ArrayList, LinkedList Queue PriorityQueue, LinkedList Map Hashtable, HashMap, LinkedHashMap, WeakHashMap, IdentityHashMap SortedMap TreeMap
- 6. Collection Framework - I Conversion of different Collection data types • Implementations of the Collection interface normally have a constructor that accepts a Collection object. • This enables you to convert a Collection to a different type of Collection, such as a Queue to a List, or a List to a Set, etc. 6
- 7. Collection Framework - I Conversion of different Collection data types constructors of some implementations • public ArrayList (Collection c) • public HashSet (Collection c) • public LinkedList (Collection c) 7
- 8. Collection Framework - I An example that converts a Queue to a List import java.util.*; public class MainClass { public static void main(String[] args) { Queue queue = new LinkedList(); queue.add("Hello"); queue.add("World"); List list = new ArrayList(queue); System.out.println(list); } // output :: [Hello, World] } 8
- 9. Collection Framework - I This example converts a List to a Set. import java.util.*; public class MainClass { public static void main(String[] args) { List myList = new ArrayList(); myList.add("Hello"); myList.add("World"); myList.add("World"); Set set = new HashSet(myList); System.out.println(set); } } 9