# Interface Set<E>

All Superinterfaces:
  `Collection<E>, Iterable<E>`

All Known Subinterfaces:
  `NavigableSet<E>, SortedSet<E>`

All Known Implementing Classes:
  `AbstractSet, ComponentSelector, HashSet, LinkedHashSet, TreeSet`

public interface Set<E> extends Collection<E>

A `Set` is a data structure which does not allow duplicate elements.

##### Since

1.2

- ## Method Summary

  Modifier and Type
  Method
  Description
  `boolean`
  `add(E object)`
  Adds the specified object to this set.
  `boolean`
  `addAll(Collection<? extends E> collection)`
  Adds the objects in the specified collection which do not exist yet in this set.
  `void`
  `clear()`
  Removes all elements from this set, leaving it empty.
  `boolean`
  `contains(Object object)`
  Searches this set for the specified object.
  `boolean`
  `containsAll(Collection<?> collection)`
  Searches this set for all objects in the specified collection.
  `boolean`
  `equals(Object object)`
  Compares the specified object to this set, and returns true if they represent the same object using a class specific comparison.
  `int`
  `hashCode()`
  Returns the hash code for this set.
  `boolean`
  `isEmpty()`
  Returns true if this set has no elements.
  `Iterator<E>`
  `iterator()`
  Returns an iterator on the elements of this set.
  `boolean`
  `remove(Object object)`
  Removes the specified object from this set.
  `boolean`
  `removeAll(Collection<?> collection)`
  Removes all objects in the specified collection from this set.
  `boolean`
  `retainAll(Collection<?> collection)`
  Removes all objects from this set that are not contained in the specified collection.
  `int`
  `size()`
  Returns the number of elements in this set.
  `Object[]`
  `toArray()`
  Returns an array containing all elements contained in this set.
  `<T> T[]`
  `toArray(T[] array)`
  Returns an array containing all elements contained in this set.

  ### Methods inherited from interface Collection

  `removeIf`

  ### Methods inherited from interface Iterable

  `forEach`

- ## Method Details

  - ### add

    boolean add(E object)

    Adds the specified object to this set. The set is not modified if it already contains the object.

    ###### Parameters

    - `object`: the object to add.

    ###### Returns

    `true` if this set is modified, `false` otherwise.

    ###### Throws

    - `UnsupportedOperationException`: when adding to this set is not supported.

    - `ClassCastException`: when the class of the object is inappropriate for this set.

    - `IllegalArgumentException`: when the object cannot be added to this set.

    Specified by:
      `add` in interface `Collection<E>`
    Returns:

      `true` if this `Collection` is modified, `false` otherwise.

      ###### Throws

      - `UnsupportedOperationException`: if adding to this `Collection` is not supported.

      - `ClassCastException`: @throws ClassCastException if the class of the object is inappropriate for this collection.

      - `IllegalArgumentException`: if the object cannot be added to this `Collection`.

      - `NullPointerException`: if null elements cannot be added to the `Collection`.

  - ### addAll

    boolean addAll(Collection<? extends E> collection)

    Adds the objects in the specified collection which do not exist yet in this set.

    ###### Parameters

    - `collection`: the collection of objects.

    ###### Returns

    `true` if this set is modified, `false` otherwise.

    ###### Throws

    - `UnsupportedOperationException`: when adding to this set is not supported.

    - `ClassCastException`: when the class of an object is inappropriate for this set.

    - `IllegalArgumentException`: when an object cannot be added to this set.

    Specified by:
      `addAll` in interface `Collection<E>`
    Returns:

      `true` if this `Collection` is modified, `false` otherwise.

      ###### Throws

      - `UnsupportedOperationException`: if adding to this `Collection` is not supported.

      - `ClassCastException`: @throws ClassCastException if the class of an object is inappropriate for this `Collection`.

      - `IllegalArgumentException`: if an object cannot be added to this `Collection`.

      - `NullPointerException`: @throws NullPointerException if `collection` is `null`, or if it contains `null` elements and this `Collection` does not support such elements.

  - ### clear

    void clear()

    Removes all elements from this set, leaving it empty.

    ###### Throws

    - `UnsupportedOperationException`: when removing from this set is not supported.

    ###### See also

    - #isEmpty

    - #size

    Specified by:
      `clear` in interface `Collection<E>`

  - ### contains

    boolean contains(Object object)

    Searches this set for the specified object.

    ###### Parameters

    - `object`: the object to search for.

    ###### Returns

    Specified by:
      `contains` in interface `Collection<E>`
    Returns:
      `true` if object is an element of this set, `false` otherwise.

  - ### containsAll

    boolean containsAll(Collection<?> collection)

    Searches this set for all objects in the specified collection.

    ###### Parameters

    - `collection`: the collection of objects.

    ###### Returns

    Specified by:
      `containsAll` in interface `Collection<E>`
    Returns:
      `true` if all objects in the specified collection are elements of this set, `false` otherwise.

  - ### equals

    boolean equals(Object object)

    Compares the specified object to this set, and returns true if they represent the same object using a class specific comparison. Equality for a set means that both sets have the same size and the same elements.

    ###### Parameters

    - `object`: the object to compare with this object.

    ###### Returns

    Specified by:
      `equals` in interface `Collection<E>`
    Overrides:
      `equals` in class `Object`
    Returns:

      boolean `true` if the object is the same as this object, and `false` if it is different from this object.

      ###### See also

      - #hashCode

  - int hashCode()

    Returns the hash code for this set. Two set which are equal must return the same value.

    ###### Returns

    the hash code of this set.

    ###### See also

    - #equals
    Specified by:
      `hashCode` in interface `Collection<E>`
    Overrides:
      `hashCode` in class `Object`

  - ### isEmpty

    boolean isEmpty()

    Returns true if this set has no elements.

    ###### Returns

    Specified by:
      `isEmpty` in interface `Collection<E>`
    Returns:

      `true` if this set has no elements, `false` otherwise.

      ###### See also

      - #size

  - ### iterator

    Iterator<E> iterator()

    Returns an iterator on the elements of this set. The elements are unordered.

    ###### Returns

    an iterator on the elements of this set.

    ###### See also

    - Iterator
    Specified by:
      `iterator` in interface `Collection<E>`
    Specified by:
      `iterator` in interface `Iterable<E>`

  - ### remove

    boolean remove(Object object)

    Removes the specified object from this set.

    ###### Parameters

    - `object`: the object to remove.

    ###### Returns

    `true` if this set was modified, `false` otherwise.

    ###### Throws

    - `UnsupportedOperationException`: when removing from this set is not supported.
    Specified by:
      `remove` in interface `Collection<E>`
    Returns:

      `true` if this `Collection` is modified, `false` otherwise.

      ###### Throws

      - `UnsupportedOperationException`: if removing from this `Collection` is not supported.

      - `ClassCastException`: if the object passed is not of the correct type.

      - `NullPointerException`: @throws NullPointerException if `object` is `null` and this `Collection` doesn't support `null` elements.

  - ### removeAll

    boolean removeAll(Collection<?> collection)

    Removes all objects in the specified collection from this set.

    ###### Parameters

    - `collection`: the collection of objects to remove.

    ###### Returns

    `true` if this set was modified, `false` otherwise.

    ###### Throws

    - `UnsupportedOperationException`: when removing from this set is not supported.
    Specified by:
      `removeAll` in interface `Collection<E>`
    Returns:

      `true` if this `Collection` is modified, `false` otherwise.

      ###### Throws

      - `UnsupportedOperationException`: if removing from this `Collection` is not supported.

      - `ClassCastException`: @throws ClassCastException if one or more elements of `collection` isn't of the correct type.

      - `NullPointerException`: @throws NullPointerException if `collection` contains at least one `null` element and this `Collection` doesn't support `null` elements.

      - `NullPointerException`: if `collection` is `null`.

  - ### retainAll

    boolean retainAll(Collection<?> collection)

    Removes all objects from this set that are not contained in the specified collection.

    ###### Parameters

    - `collection`: the collection of objects to retain.

    ###### Returns

    `true` if this set was modified, `false` otherwise.

    ###### Throws

    - `UnsupportedOperationException`: when removing from this set is not supported.
    Specified by:
      `retainAll` in interface `Collection<E>`
    Returns:

      `true` if this `Collection` is modified, `false` otherwise.

      ###### Throws

      - `UnsupportedOperationException`: if removing from this `Collection` is not supported.

      - `ClassCastException`: @throws ClassCastException if one or more elements of `collection` isn't of the correct type.

      - `NullPointerException`: @throws NullPointerException if `collection` contains at least one `null` element and this `Collection` doesn't support `null` elements.

      - `NullPointerException`: if `collection` is `null`.

  - ### size

    int size()

    Returns the number of elements in this set.

    ###### Returns

    the number of elements in this set.

    Specified by:
      `size` in interface `Collection<E>`
    Returns:
      how many objects this `Collection` contains, or Integer.MAX_VALUE if there are more than Integer.MAX_VALUE elements in this `Collection`.

  - ### toArray

    Object[] toArray()

    Returns an array containing all elements contained in this set.

    ###### Returns

    an array of the elements from this set.

    Specified by:
      `toArray` in interface `Collection<E>`

  - ### toArray

    <T> T[] toArray(T[] array)

    Returns an array containing all elements contained in this set. If the specified array is large enough to hold the elements, the specified array is used, otherwise an array of the same type is created. If the specified array is used and is larger than this set, the array element following the collection elements is set to null.

    ###### Parameters

    - `array`: the array.

    ###### Returns

    an array of the elements from this set.

    ###### Throws

    - `ArrayStoreException`: @throws ArrayStoreException when the type of an element in this set cannot be stored in the type of the specified array.

    ###### See also

    - Collection#toArray(Object[])
    Specified by:
      `toArray` in interface `Collection<E>`