# Basics of Set

suggest change**What is a Set?**

A set is a data structure which contains a set of elements with an important property that no two elements in the set are equal.

**Types of Set:**

**HashSet:**A set backed by a hash table (actually a HashMap instance)**Linked HashSet:**A Set backed by Hash table and linked list, with predictable iteration order**TreeSet:**A NavigableSet implementation based on a TreeMap.

**Creating a set**

```
Set<Integer> set = new HashSet<Integer>(); // Creates an empty Set of Integers
Set<Integer> linkedHashSet = new LinkedHashSet<Integer>(); //Creates a empty Set of Integers, with predictable iteration order
```

**Adding elements to a Set**

Elements can be added to a set using the `add()`

method

```
set.add(12); // - Adds element 12 to the set
set.add(13); // - Adds element 13 to the set
```

Our set after executing this method:

`set = [12,13]`

**Delete all the elements of a Set**

`set.clear(); //Removes all objects from the collection.`

After this set will be:

`set = []`

**Check whether an element is part of the Set**

Existence of an element in the set can be checked using the `contains()`

method

`set.contains(0); //Returns true if a specified object is an element within the set.`

**Output:** `False`

**Check whether a Set is empty**

`isEmpty()`

method can be used to check whether a Set is empty.

`set.isEmpty(); //Returns true if the set has no elements`

**Output:** True

**Remove an element from the Set**

`set.remove(0); // Removes first occurrence of a specified object from the collection`

**Check the Size of the Set**

`set.size(); //Returns the number of elements in the collection`

**Output:** 0

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