Hash set in Java

HashSet is a class in the Java Collections Framework that implements the Set interface to create an unordered collection of unique elements. In other words, it cannot contain duplicate elements, and the elements are not stored in any particular order. HashSet internally uses a ha

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Here are some of the key features of HashSet:

1. Uniqueness: HashSet guarantees that there are no duplicate elements. If you try to add an element that already exists in the set, the new element will not be added.
2. Null elements: HashSet allows one null element to be added to the set. If you try to add more than one null element, it will throw a NullPointerException.
3. Ordering: HashSet does not maintain any order for its elements. Elements are stored randomly, so the order of elements in the set may change over time.
4. Performance: HashSet offers constant-time performance for adding, removing, and searching for elements on average (assuming a good hash function). However, the actual performance may vary depending on the size of the set and the hash function used.

Here’s an example of how to create a HashSet, add elements to it, and iterate over the elements:

HashSet<String> set = new HashSet<>();

// Adding elements to the set
set.add("apple");
set.add("banana");
set.add("cherry");
set.add("orange");

// Printing out the elements in the set
for (String element : set) {
    System.out.println(element);
}

This will output the following:

banana
orange
cherry
apple

Note that the order of the elements in the HashSet is not guaranteed to be the same as the order in which they were added.

HashSet is not synchronized, which means that it is not thread-safe. If multiple threads access a HashSet concurrently and at least one of the threads modifies the set, it must be synchronized externally. You can create a synchronized version of HashSet by using the Collections.s

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Set<String> synchronizedSet = Collections.synchronizedSet(new HashSet<>());

This will return a thread-safe Set that can be safely accessed by multiple threads.