HashSet vs LinkedHashSet

difference between hashset and linkedhashset javatpoint
hashset vs linkedhashset javatpoint
hashset vs treeset
hashset vs hashmap
linkedhashset duplicates
hashmap vs linkedhashmap
linkedhashset to list
arraylist vs linkedlist

What is the difference between them? I know that

A LinkedHashSet is an ordered version of HashSet that maintains a doubly-linked List across all elements. Use this class instead of HashSet when you care about the iteration order. When you iterate through a HashSet the order is unpredictable, while a LinkedHashSet lets you iterate through the elements in the order in which they were inserted.

But in sourcecode of LinkedHashSet there are only calling constructors of HashSet. So where is double-linked List and insertion order?

The answer lies in which constructors the LinkedHashSet uses to construct the base class:

public LinkedHashSet(int initialCapacity, float loadFactor) {
    super(initialCapacity, loadFactor, true);      // <-- boolean dummy argument


public LinkedHashSet(int initialCapacity) {
    super(initialCapacity, .75f, true);            // <-- boolean dummy argument


public LinkedHashSet() {
    super(16, .75f, true);                         // <-- boolean dummy argument


public LinkedHashSet(Collection<? extends E> c) {
    super(Math.max(2*c.size(), 11), .75f, true);   // <-- boolean dummy argument

And (one example of) a HashSet constructor that takes a boolean argument is described, and looks like this:

 * Constructs a new, empty linked hash set.  (This package private
 * constructor is only used by LinkedHashSet.) The backing
 * HashMap instance is a LinkedHashMap with the specified initial
 * capacity and the specified load factor.
 * @param      initialCapacity   the initial capacity of the hash map
 * @param      loadFactor        the load factor of the hash map
 * @param      dummy             ignored (distinguishes this
 *             constructor from other int, float constructor.)
 * @throws     IllegalArgumentException if the initial capacity is less
 *             than zero, or if the load factor is nonpositive
HashSet(int initialCapacity, float loadFactor, boolean dummy) {
    map = new LinkedHashMap<E,Object>(initialCapacity, loadFactor);

Difference and similarities between HashSet, LinkedHashSet and , Comparison of LinkedHashSet and HashSet performance is not correct. The LinkedHashSet insertion is slightly slower, and uses slightly more  HashSet VS LinkedHashSet Java: HashSet class implements the Set interface, it uses a hashtable to store the elements and contains only unique elements 2020 ️

LinkedHashSet's constructors invoke the following base class constructor:

HashSet(int initialCapacity, float loadFactor, boolean dummy) {
  map = new LinkedHashMap<E, Object>(initialCapacity, loadFactor);

As you can see, the internal map is a LinkedHashMap. If you look inside LinkedHashMap, you'll discover the following field:

private transient Entry<K, V> header;

This is the linked list in question.

HashSet Vs TreeSet Vs LinkedHashSet In Java, maintains objects in Sorted order defined by either Comparable or Comparator method in Java. HashSet performance is better according to LinkedHashSet and TreeSet. The performance of LinkedHashSet is slow to TreeSet. The performance LinkedHashSet is almost similar to HashSet but slower because, LinkedHashSet maintains LinkedList internally to maintain the insertion order of elements

HashSet is unordered and unsorted Set. LinkedHashSet is the ordered version of HashSet.

The only difference between HashSet and LinkedHashSet is that: LinkedHashSet maintains the insertion order.

When we iterate through a HashSet, the order is unpredictable while it is predictable in case of LinkedHashSet.

The reason for how LinkedHashSet maintains insertion order is that: The underlying used data structure is Doubly-Linked-List.

Java: Hashset Vs TreeSet when should i use over other, is needed to be maintained this class is used. Null elements HashSet allows to store one null in java. LinkedHashSet allows to store one null in java. TreeSet does not allows to store any null in java.

You should look at the source of the HashSet constructor it calls... it's a special constructor that makes the backing Map a LinkedHashMap instead of just a HashMap.

LinkedHashSet in Java with Examples, is two objects that are equal to each other, according to their equals() method. So you need to add a more specific implementation of equals (and hashcode ) for your class. HashSet Vs LinkedHashSet Vs TreeSet in Java. First and most important difference is related to the ordering of the elements. HashSet is unordered, it will store elements on the basis of the calculated hash that's it. LinkedHashSet maintains the insertion ordering of the elements. TreeSet keeps the element in sorted order. The sorting orders TreeSet follows by default is the natural ordering of the elements.

I suggest you to use LinkedHashSet most of the time, because it has better performance overall):

  1. Predictable iteration order LinkedHashSet (Oracle)
  2. LinkedHashSet is more expensive for insertions than HashSet;
  3. In general slightly better performance than HashMap, because the most of the time we use Set structures for iterating.

Performance tests:

------------- TreeSet -------------
 size       add  contains   iterate
   10       746       173        89
  100       501       264        68
 1000       714       410        69
10000      1975       552        69
------------- HashSet -------------
 size       add  contains   iterate
   10       308        91        94
  100       178        75        73
 1000       216       110        72
10000       711       215       100
---------- LinkedHashSet ----------
 size       add  contains   iterate
   10       350        65        83
  100       270        74        55
 1000       303       111        54
10000      1615       256        58

You can see source test page here: The Final Performance Testing Example

LinkedHashSet remove duplicates object, to initialize both the capacity and the fill ratio (also called load capacity) of the hash set from its argument. HashSet is fastest, LinkedHashSet is second on performance or almost similar to HashSet but TreeSet is bit slower because of sorting operation it needs to perform on each insertion.

LinkedHashSet in Java, TreeSet vs HashSet vs LinkedHashSet - Example. Let's compare all these Set implementation on some points by writing Java program. In this  Operation: LinkedHashMap does a mapping of keys to values while LinkedHashSet simply stores a collection of things. Null Object: LinkedHashMap have elements in key value pair so have only one null key and multiple null value, while LinkedHashSet simply stores a collection of things with one null value.

Difference between TreeSet, LinkedHashSet and , HashSet is faster than both LinkedHashSet and TreeSet as LinkedHashSet has the overhead of maintaining the insertion order and TreeSet has the overhead of​  HashSet(Collection c) This constructor initializes the hash set by using the elements of the collection c. 3: 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. 4: LinkedHashSet(int capacity, float fillRatio)

HashSet vs. TreeSet vs. LinkedHashSet, LinkedHashSet, TreeSet, and HashSet are three of most popular implementation of Set interface in Java Collection Framework. Since they implement Set