Explain HashSet, LinkedHashSet and TreeSet
Explanation
1. HashSet
- Structure: HashSet is a collection that does not allow duplicate elements. It is backed by a hash table (actually a HashMap instance).
- Ordering: HashSet does not guarantee any specific iteration order of the elements.
- Performance: Provides constant time performance for basic operations like add, remove, contains, and size, assuming the hash function disperses elements properly among the buckets.
2. LinkedHashSet
- Structure: LinkedHashSet extends HashSet but maintains a doubly-linked list running through all of its entries.
- Ordering: This linked list defines the iteration ordering, which is the order in which elements were inserted into the set (insertion-order).
- Performance: Offers performance similar to HashSet but with a slightly overhead for maintaining the linked list.
3. TreeSet
- Structure: TreeSet is a NavigableSet implementation based on a TreeMap.
- Ordering: It stores elements in a sorted and ascending order according to their natural ordering or by a specified comparator.
- Erformance: Provides guaranteed log(n) time cost for the basic operations (add, remove, and contains).
Table of Contents
java
Here's a Java example demonstrating the differences between these three sets:
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.TreeSet;
public class SetExample {
public static void main(String[] args) {
// HashSet Example
HashSet<String> hashSet = new HashSet<>();
hashSet.add("Banana");
hashSet.add("Apple");
hashSet.add("Cherry");
hashSet.add("Date");
System.out.println("HashSet: " + hashSet);
// LinkedHashSet Example
LinkedHashSet<String> linkedHashSet = new LinkedHashSet<>();
linkedHashSet.add("Banana");
linkedHashSet.add("Apple");
linkedHashSet.add("Cherry");
linkedHashSet.add("Date");
System.out.println("LinkedHashSet: " + linkedHashSet);
// TreeSet Example
TreeSet<String> treeSet = new TreeSet<>();
treeSet.add("Banana");
treeSet.add("Apple");
treeSet.add("Cherry");
treeSet.add("Date");
System.out.println("TreeSet: " + treeSet);
}
}
Explanation HashSet , LinkedHashSet and TreeSet
- The HashSet does not guarantee the order of elements. When you print the HashSet, the elements may not appear in the order you inserted them.
- Example output: HashSet: [Banana, Cherry, Apple, Date]
- LinkedHashSet:
- The LinkedHashSet maintains the insertion order. When you print the LinkedHashSet, the elements will appear in the order you inserted them.
Example output
- LinkedHashSet: [Banana, Apple, Cherry, Date]
- TreeSet:
- The TreeSet maintains the elements in a sorted order. When you print the TreeSet, the elements will appear sorted in ascending order.
- Example output: TreeSet: [Apple, Banana, Cherry, Date]