Hash set and tree set both belong to the collection framework. HashSet is the implementation of the Set interface whereas Tree set implements sorted set. Tree set is backed by TreeMap while HashSet is backed by a hashmap.
| Sr. No. | Key | Hash Set | Tree Set |
|---|---|---|---|
| 1 | Implementation | Hash set is implemented using HashTable | The tree set is implemented using a tree structure. |
| 2 | Null Object | HashSet allows a null object | The tree set does not allow the null object. It throws the null pointer exception. |
| 3 | Methods | Hash set use equals method to compare two objects | Tree set use compare method for comparing two objects. |
| 4 | Heterogeneous object | Hash set doesn't now allow a heterogeneous object | Tree set allows a heterogeneous object |
| 5 | Ordering | HashSet does not maintain any order | TreeSet maintains an object in sorted order |
Example of TreeSet
class TreeSetExmaple {
public static void main(String[] args){
TreeSet<String> treeset = new TreeSet<String>();
treeset.add("Good");
treeset.add("For");
treeset.add("Health");
//Add Duplicate Element
treeset.add("Good");
System.out.println("TreeSet : ");
for (String temp : treeset) {
System.out.println(temp);
}
}
}Output
TreeSet: For Good Health
Example of HashSet
class HashSetExample {
public static void main(String[] args){
HashSet<String> hashSet = new HashSet<String>();
hashSet.add("Good");
hashSet.add("For");
hashSet.add("Health");
//Add Duplicate Element
hashSet.add("Good");
System.out.println("HashSet: ");
for (String temp : hashSet) {
System.out.println(temp);
}
}
}Output
HashSet: Health For Good