LinkedHashSet in Java with Examples

A LinkedHashSet is an ordered version of HashSet that maintains a doubly-linked List across all elements. When the iteration order is needed to be maintained this class is used. When iterating through a HashSet the order is unpredictable, while a LinkedHashSet lets us iterate through the elements in the order in which they were inserted. When cycling through LinkedHashSet using an iterator, the elements will be returned in the order in which they were inserted.

Syntax:

LinkedHashSet<String> hs = new LinkedHashSet<String>();

• It contains unique elements only like HashSet. It extends the HashSet class and implements the Set interface.
• Maintains insertion order.

Given below are the list of constructors supported by the LinkedHashSet:

1. LinkedHashSet(): This constructor is used to create a default HashSet.
2. LinkedHashSet(Collection C): Used in initializing the HashSet with the elements of the collection C
3. LinkedHashSet(int size): Used to initialize the size of the LinkedHashSet with the integer mentioned in the parameter.
4. LinkedHashSet(int capacity, float filtration): Can be used to initialize both the capacity and the fill ratio, also called the load capacity of the LinkedHashSet with the arguments mentioned in the parameter. When the number of elements exceeds the capacity of the hash set is multiplied with the fill ratio thus expanding the capacity of the LinkedHashSet

Methods in LinkedHashSet:

1. spliterator? (): This method creates a late-binding and fail-fast Spliterator over the elements in this set.
2. clear? (): This method removes all of the elements from this set.
3. contains? (Object o): This method returns true if this set contains the specified element.

Below program explains the basic add and traversal operation of LinkedHashSet:

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Output:

Size of LinkedHashSet=5
Original LinkedHashSet:[A, B, C, D, E]
Removing D from LinkedHashSet: true
Trying to Remove Z which is not present: false
Checking if A is present=true
Updated LinkedHashSet: [A, B, C, E]

Following is the difference between LinkedHashMap and LinkedHashSet:

Important: Keeping the insertion order in both LinkedHashmap and LinkedHashset have additional associated costs, both in terms of spending additional CPU cycles and needing more memory. If you do not need the insertion order maintained, it is recommended to use the lighter-weight HashSet and HashMap instead.