Learn LinkedHashSet Class in Java with Programming Example

In this chapter you will learn:

What is LinkedHashSet Class in Java
Declaration and Methods of LinkedHashSet Class
Programming Example

What is LinkedHashSet Class in Java?

LinkedHashSet is an implementation of HashSet in a linked list with predictable iteration order. It is different from HashSet as it maintains doubly linked list through its all entries. Linked list maintain the insertion order so the items are stored in Linked Hash Table as the order they inserted. It inherits all the methods of set operation and allow null element entry.

Constructors

Constructors	Descriptions
`LinkedHashSet()`	Constructs a new, empty linked hash set with the default initial capacity (16) and load factor (0.75).
`LinkedHashSet(Collection<? extends E> c)`	Constructs a new linked hash set with the same elements as the specified collection.
`LinkedHashSet(int initialCapacity)`	Constructs a new, empty linked hash set with the specified initial capacity and the default load factor (0.75).
`LinkedHashSet(int initialCapacity, float loadFactor)`	Constructs a new, empty linked hash set with the specified initial capacity and load factor.

Methods Inherited From Class

Class	Methods
`java.util.HashSet`	add(), clear(), clone(), contains(), isEmpty(), iterator(), remove(), size()
`java.util.AbstractSet`	equals(), hashCode(), removeAll()
`java.util.AbstractCollection`	addAll(), containsAll(), retainAll(), toArray(), toArray(), toString()
`java.lang.Object`	finalize(), getClass(), notify(), notifyAll(), wait(), wait(), wait()
`java.util.Set`	add(), addAll(), clear(), contains(), containsAll(), equals(), hashCode(), isEmpty(), iterator(), remove(), removeAll(), retainAll(), size(), toArray(), toArray()

Declaration:

LinkedHashSet hs=new LinkedHashSet();

Programming Example

import java.util.*;
class LinkedHashSet_Example
{
  public static void main(String[] args)
  {
    //Declaring LinkedHashSet
    LinkedHashSet hs=new LinkedHashSet();
    
    //Adding Item
    hs.add("C#");
    hs.add("Java");
    hs.add("SQL");
    hs.add("PHP");
    hs.add("HTML");
    
    //Printing LinkedHashSet
    Iterator itr=hs.iterator();
    while(itr.hasNext())
    {
      System.out.print(itr.next() + " ");
    }
    
    //Removing an Item
    System.out.println("\nItem Removed : "+ hs.remove("SQL"));
    
    //Printing 
    System.out.println(hs);
  }
}

Output

D:\JavaProgram>javac LinkedHashSet_Example.java
D:\JavaProgram>java LinkedHashSet_ExampleC# Java SQL PHP HTML
Item Removed : true
[C#, Java, PHP, HTML]
_

Summary

In this chapter you learned LinkedHashSet class in java with programming example. In the next chapter you will learn TreeSet Class in Java.

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