Java LinkedHashSet

Java LinkedHashSet
Syntax:
java.lang.Object
     java.util.AbstractCollection
         java.util.AbstractSet
             java.util.HashSet
                 java.util.LinkedHashSet

• Note: E - the type of elements maintained by this set

• The LinkedHashSet class has no members of its own.
• Java LinkedHashSet class is a Hashtable and Linked list implementation of the Set interface. 
  
• A LinkedHashSet is an ordered version of HashSet that maintains a doubly-linked List across all elements.
• The hash code is then used as the index at which the data associated with the key is stored. 
• The transformation of the key into its hash code is performed automatically.
• The LinkedHashSet does not allow duplicate elements and it does not maintain order.
• The difference between them is...
• HashSet doesn’t maintain any kind of order of its elements.
• TreeSet sorts the elements in ascending order.
• LinkedHashSet maintains the insertion order and Elements gets sorted in the same sequence in which they have been added to the Set.

Constructors:

• HashSet( ): This constructor constructs a default HashSet.
• HashSet(Collection c): This constructor initializes the hash set by using the elements of the collection c.
• LinkedHashSet(int capacity): This constructor initializes the capacity of the linkedhashset to the given integer value capacity. The capacity grows automatically as elements are added to the HashSet.
• LinkedHashSet(int capacity, float fillRatio): This constructor initializes both the capacity and the fill ratio (also called load capacity) of the hash set from its arguments.

Methods:

• How to declare object of LinkedHashSet?
• Syntax:

LinkedHashSet lhset = new LinkedHashSet();

• Example:

//non-generic
LinkedHashSet hs = new LinkedHashSet();
//Integer type
LinkedHashSet lhset1 = new LinkedHashSet();
//String type
LinkedHashSet lhset2 = new LinkedHashSet();

• How to add new elements in LinkedHashSet?
• Syntax:

         object-name.add(string);

• Example: 

         lhset1.add(99);
         lhset2.add("PQ");

• How to display all elements from LinkedHashSet?
• Example:

System.out.println(lhset1);
System.out.println(lhset2);

• How to display all elements using iterator?
• Example:

Iterator i=lhset1.iterator();  
while(i.hasNext())
{
System.out.println(i.next());
}

• How to remove an element from LinkedHashSet?
• Example:

lhset1.remove(99)

• How to check given element is present or not?
• Example:

System.out.println("Checking if 99 is present);
System.out.println(lhset1.contains(99));

• How to get the size of LinkedHashSet?
• Example:

lhset1.size()