The HashSet
class is a general set class that implements the Set interface. The elements are stored in a hash table that allows quick access.
It is generally used when no mapping of keys to pairs of values is required, unlike the HashMap.
import java.util.HashSet;
HashSet<String> hashSet = new HashSet<String>();
import java.util.HashSet;
import java.util.Iterator;
class HashSet {
public static void main(String[] args) {
HashSet<String> set = new HashSet<String>();
set.add("First");
set.add("Second");
set.add("Third");
set.add("Fourth");
boolean isEmpty = set.isEmpty();
int size = set.size();
boolean containsEntry = set.contains("Third");
set.remove("Fourth");
System.out.println("isEmpty: " + isEmpty);
System.out.println("size: " + size);
System.out.println("containsEntry: " + containsEntry);
// output elements using enhanced for loop
for (String s : set) {
System.out.println(s);
}
// output elements using iterator
System.out.println("\nIterator output");
Iterator<String> iter = set.iterator();
while (iter.hasNext()) {
System.out.println(iter.next());
}
}
}
isEmpty: false
size: 4
containsEntry: true
Second
Third
First
Iterator output
Second
Third
First