Lecture Notes: LinkedHashSet in Java

Introduction

• Topic: Understanding the concept of LinkedHashSet in Java.
• Context: Builds on previous discussions about the Collection interface and its child interfaces and classes.
  • Collection Interface: Root interface of all collections.
  • Set Interface: Child interface of Collection.
  • Classes Implementing Set: HashSet and LinkedHashSet.

LinkedHashSet vs. HashSet

Similarities

• Both HashSet and LinkedHashSet implement the Set interface.
• Neither allows duplicate elements.
• Both can configure initial size and load factor (default is 16 and 0.71 respectively).

Differences

• HashSet:
  • Insertion order is not preserved (elements are stored in random order).
  • Underlying data structure: Hash Table.
• LinkedHashSet:
  • Preserves insertion order (elements are stored in the order they are inserted).
  • Underlying data structure: Combination of Hash Table and Linked List.

Implementation Details

Creating a LinkedHashSet

• Declaration: LinkedHashSet<Integer> lSet = new LinkedHashSet<>();
  • Can specify data type to store similar types of objects (e.g., Integer).
  • Can opt for storing different types without specifying a data type.

Adding Elements

• Use the add method to insert elements.
  • Example: lSet.add(100); for inserting integers.
• Properties:
  • Duplicates are not allowed.
  • Insertion order is preserved.

Demo

• HashSet Behavior:
  • Random element order upon printing.
  • Example output may differ from insertion order.
• LinkedHashSet Behavior:
  • Maintains insertion order upon printing.
  • Demonstrates the key difference in maintaining order.

Methods

• Methods available in HashSet are also applicable to LinkedHashSet:
  • add, addAll, remove, removeAll, contains, and containsAll.

Conclusion

• Core Understanding: LinkedHashSet is primarily distinguished from HashSet by its ability to preserve the insertion order of elements.
• Practical application of LinkedHashSet is demonstrated through code examples using Eclipse IDE.

This concludes the lecture on LinkedHashSet in Java.