HashSet Class
In this tutorial, we are going to discuss HashSet class in java. This class implements the Set interface, backed by a hash table (actually a HashMap instance).
- The underlying data structure is the Hash table.
- Insertion order is not preserved, and it is based on the hash code of the objects.
- Duplicate objects are not allowed.
- If we are trying to insert duplicate objects, we won’t get a compile-time error, and the runtime error add() method simply returns false.
- Heterogeneous objects are allowed.
- Null insertion is possible. (only once)
- HashSet is non-synchronized.
- Implements Serializable and Cloneable interfaces but not RandomAccess.
- HashSet is best suitable if our frequent operation is “Search.”
![HashSet Class](https://waytoeasylearn.com/storage/2021/11/Hashset.png)
Constructors
1. HashSet h = new HashSet()
Creates an empty HashSet object with default initial value 16 and default fill ratio 0.75
2. HashSet h = new HashSet(int initialcapacity)
3. HashSet h = new HashSet(int initialCapacity, float fillratio)
Here fillratio is 0 or 1.
4. HashSet h = new HashSet(Collection c)
Note
After filling how much ratio new HashSet object will be created , The ratio is called “FillRatio” or “LoadFactor“.
package com.ashok.collections.hashset;
import java.util.HashSet;
/**
*
* @author ashok.mariyala
*
*/
public class MyHashSet {
public static void main(String args[]) {
// HashSet declaration
HashSet<string> hset = new HashSet<string>();
// Adding elements to the HashSet
hset.add("Ashok");
hset.add("Vinod");
hset.add("Dillesh");
hset.add("Thiru");
hset.add("Naresh");
System.out.println(hset);
// Addition of duplicate elements
System.out.println(hset.add("Ashok"));
System.out.println(hset);
// Addition of null values
hset.add(null);
System.out.println(hset.add(null));
// Displaying HashSet elements
System.out.println(hset);
}
}
Output
[Thiru, Ashok, Dillesh, Vinod, Naresh]
false
[Thiru, Ashok, Dillesh, Vinod, Naresh]
false
[null, Thiru, Ashok, Dillesh, Vinod, Naresh]
That’s all about the HashSet Class in java. If you have any queries or feedback, please write us email at contact@waytoeasylearn.com. Enjoy learning, Enjoy Java.!!
HashSet Class