LinkedHashSet – Internal implementation
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LinkedHashSet is an extended version of HashSet. HashSet doesn’t follow any order where as LinkedHashSet maintains insertion order
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HashSet uses HashMap object internally to store its elements where as LinkedHashSet uses LinkedHashMap object internally to store and process it’s elements
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LinkedHashSet, elements you insert are stored as keys of LinkedHashMap object. The values of these keys will be the same constant i.e -PRESENT-.
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The insertion order of elements into LinkedHashMap are maintained by adding two new fields to this class. They are before and after. These two fields hold the references to previous and next elements. These two fields make LinkedHashMap to function as a doubly linked list.
public class HashSetDemo {
public static void main(String[] args) {
LinkedHashSet h = new LinkedHashSet();
h.add("A");
h.add("B");
h.add("C");
h.add(10);
h.add(null);
System.out.println(h.add("A"));
System.out.println(h);
}
}
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false
[A, B, C, 10, null]
