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Java Programming LinkedHashSet

What is LinkedHashSet?

LinkedHashSet is also an implementation of Set interface, it is similar to the HashSet and TreeSet except the below mentioned differences:

  • HashSet doesn’t maintain any kind of order of its elements.
  • TreeSet sorts the elements in ascending order.
  • LinkedHashSet maintains the insertion order.
  • Elements gets sorted in the same sequence in which they have been added to the Set.

How to perform Basic Operations in LinkedHashSet ?

The Basic Operations are:

  • Create LinkedHashSet object
  • Adding elements to it
  • Getting size of LinkedHashSet object
  • Is the set empty or not

Basic Operations

import java.util.LinkedHashSet;
 
public class Demo {
 
    public static void main(String a[]){
         
        LinkedHashSet s1 = new LinkedHashSet();
        s1.add("first");
        s1.add("second");
        s1.add("third");
        System.out.println(s1);
        System.out.println("LinkedHashSet size: "+s1.size());
        System.out.println("Is LinkedHashSet emplty? : "+s1.isEmpty());
    }
}
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How to add another collection to LinkedHashSet?

By using addAll() method, we can add all elements from another collection object.

Example

import java.util.HashSet;
import java.util.LinkedHashSet;
 
public class Demo {
 
    public static void main(String a[]){
         
        LinkedHashSet s1 = new LinkedHashSet();
        s1.add("first");
        s1.add("second");
        s1.add("third");
        System.out.println(s1);
        HashSet subSet = new HashSet();
        subSet.add("s1");
        subSet.add("s2");
        s1.addAll(subSet);
        System.out.println("LinkedHashSet content after adding another collection:");
        System.out.println(s1);
    }
}
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How to delete all elements from LinkedHashSet?

By using clear() method, we can delete all elements at once.

Example

import java.util.LinkedHashSet;
 
public class Demo {
 
    public static void main(String a[]){
         
        LinkedHashSet s1 = new LinkedHashSet();
        s1.add("first");
        s1.add("second");
        s1.add("third");
        System.out.println("My LinkedHashSet content:");
        System.out.println(s1);
        System.out.println("Clearing LinkedHashSet:");
        s1.clear();
        System.out.println("Content After clear:");
        System.out.println(s1);
    }
}
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How to iterate through LinkedHashSet?

By calling iterator() method you will get Iterator object, through which you can iterate all the elements of the LinkedHashSet.

Example

import java.util.Iterator;
import java.util.LinkedHashSet;
 
public class Demo {
 
    public static void main(String a[]){
        LinkedHashSet s1 = new LinkedHashSet();
        s1.add("first");
        s1.add("second");
        s1.add("third");
        Iterator itr = s1.iterator();
        while(itr.hasNext()){
            System.out.println(itr.next());
        }
    }
}
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How to copy content of LinkedHashSet to an array?

Example

public class Demo {
 
    public static void main(String a[]){
         
        LinkedHashSet s1 = new LinkedHashSet();
        s1.add("first");
        s1.add("second");
        s1.add("third");
        System.out.println("LinkedHashSet content: ");
        System.out.println(s1);
        String[] strArr = new String[s1.size()];
        s1.toArray(strArr);
        System.out.println("Copied array content:");
        for(String str:strArr){
            System.out.println(str);
        }
    }
}
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