Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) Summary: [Ctors](https://developer.android.com/reference/java/util/LinkedHashSet#pubctors) \| [Methods](https://developer.android.com/reference/java/util/LinkedHashSet#pubmethods) \| [Inherited Methods](https://developer.android.com/reference/java/util/LinkedHashSet#inhmethods)

# LinkedHashSet


`
public


class
LinkedHashSet
`


`


`

`


`

`


`

`

extends https://developer.android.com/reference/java/util/HashSet<E>


`

`


implements

https://developer.android.com/reference/java/lang/Cloneable,

https://developer.android.com/reference/java/util/SequencedSet<E>,

https://developer.android.com/reference/java/io/Serializable,

https://developer.android.com/reference/java/util/Set<E>


`

|---|---|---|---|---|
| [java.lang.Object](https://developer.android.com/reference/java/lang/Object) |||||
| ↳ | [java.util.AbstractCollection](https://developer.android.com/reference/java/util/AbstractCollection)\<E\> ||||
|   | ↳ | [java.util.AbstractSet](https://developer.android.com/reference/java/util/AbstractSet)\<E\> |||
|   |   | ↳ | [java.util.HashSet](https://developer.android.com/reference/java/util/HashSet)\<E\> ||
|   |   |   | ↳ | java.util.LinkedHashSet\<E\> |

<br />

*** ** * ** ***

<br />

Hash table and linked list implementation of the `Set` interface,
with well-defined encounter order. This implementation differs from
`HashSet` in that it maintains a doubly-linked list running through
all of its entries. This linked list defines the encounter order (iteration
order), which is the order in which elements were inserted into the set
(*insertion-order*). The least recently inserted element (the eldest) is
first, and the youngest element is last. Note that encounter order is *not* affected
if an element is *re-inserted* into the set with the `add` method.
(An element `e` is reinserted into a set `s` if `s.add(e)` is
invoked when `s.contains(e)` would return `true` immediately prior to
the invocation.) The reverse-ordered view of this set is in the opposite order, with
the youngest element appearing first and the eldest element appearing last. The encounter
order of elements already in the set can be changed by using the
`https://developer.android.com/reference/java/util/LinkedHashSet#addFirst(E)` and `https://developer.android.com/reference/java/util/LinkedHashSet#addLast(E)` methods.

This implementation spares its clients from the unspecified, generally
chaotic ordering provided by `https://developer.android.com/reference/java/util/HashSet`, without incurring the
increased cost associated with `https://developer.android.com/reference/java/util/TreeSet`. It can be used to
produce a copy of a set that has the same order as the original, regardless
of the original set's implementation:

    void foo(Set<String> s) {
            Set<String> copy = new LinkedHashSet<>(s);
            ...
        }

This technique is particularly useful if a module takes a set on input, copies it, and later returns results whose order is determined by that of the copy. (Clients generally appreciate having things returned in the same order they were presented.)

This class provides all of the optional `https://developer.android.com/reference/java/util/Set` and `https://developer.android.com/reference/java/util/SequencedSet`
operations, and it permits null elements. Like `HashSet`, it provides constant-time
performance for the basic operations (`add`, `contains` and
`remove`), assuming the hash function disperses elements
properly among the buckets. Performance is likely to be just slightly
below that of `HashSet`, due to the added expense of maintaining the
linked list, with one exception: Iteration over a `LinkedHashSet`
requires time proportional to the *size* of the set, regardless of
its capacity. Iteration over a `HashSet` is likely to be more
expensive, requiring time proportional to its *capacity*.

A linked hash set has two parameters that affect its performance:
*initial capacity* and *load factor*. They are defined precisely
as for `HashSet`. Note, however, that the penalty for choosing an
excessively high value for initial capacity is less severe for this class
than for `HashSet`, as iteration times for this class are unaffected
by capacity.

**Note that this implementation is not synchronized.**
If multiple threads access a linked hash set concurrently, and at least
one of the threads modifies the set, it *must* be synchronized
externally. This is typically accomplished by synchronizing on some
object that naturally encapsulates the set.

If no such object exists, the set should be "wrapped" using the
`https://developer.android.com/reference/java/util/Collections#synchronizedSet(java.util.Set<T>)`
method. This is best done at creation time, to prevent accidental
unsynchronized access to the set:

```
  Set s = Collections.synchronizedSet(new LinkedHashSet(...));
```

The iterators returned by this class's `iterator` method are
*fail-fast* : if the set is modified at any time after the iterator
is created, in any way except through the iterator's own `remove`
method, the iterator will throw a `https://developer.android.com/reference/java/util/ConcurrentModificationException`.
Thus, in the face of concurrent modification, the iterator fails quickly
and cleanly, rather than risking arbitrary, non-deterministic behavior at
an undetermined time in the future.

Note that the fail-fast behavior of an iterator cannot be guaranteed
as it is, generally speaking, impossible to make any hard guarantees in the
presence of unsynchronized concurrent modification. Fail-fast iterators
throw `ConcurrentModificationException` on a best-effort basis.
Therefore, it would be wrong to write a program that depended on this
exception for its correctness: *the fail-fast behavior of iterators should be used only to detect bugs.*

This class is a member of the
[Java Collections Framework](https://reference/java/util/package-summary.html#CollectionsFramework).
**See also:**

- `https://developer.android.com/reference/java/lang/Object#hashCode()`
- `https://developer.android.com/reference/java/util/Collection`
- `https://developer.android.com/reference/java/util/Set`
- `https://developer.android.com/reference/java/util/HashSet`
- `https://developer.android.com/reference/java/util/TreeSet`
- `https://developer.android.com/reference/java/util/Hashtable`

## Summary

| ### Public constructors ||
|---|---|
| ` https://developer.android.com/reference/java/util/LinkedHashSet#LinkedHashSet()() ` Constructs a new, empty linked hash set with the default initial capacity (16) and load factor (0.75). |
| ` https://developer.android.com/reference/java/util/LinkedHashSet#LinkedHashSet(int)(int initialCapacity) ` Constructs a new, empty linked hash set with the specified initial capacity and the default load factor (0.75). |
| ` https://developer.android.com/reference/java/util/LinkedHashSet#LinkedHashSet(int,%20float)(int initialCapacity, float loadFactor) ` Constructs a new, empty linked hash set with the specified initial capacity and load factor. |
| ` https://developer.android.com/reference/java/util/LinkedHashSet#LinkedHashSet(java.util.Collection<?%20extends%20E>)(https://developer.android.com/reference/java/util/Collection<? extends E> c) ` Constructs a new linked hash set with the same elements as the specified collection. |

| ### Public methods ||
|---|---|
| ` void` | ` https://developer.android.com/reference/java/util/LinkedHashSet#addFirst(E)(E e) ` Adds an element as the first element of this collection (optional operation). If this set already contains the element, it is relocated if necessary so that it is first in encounter order. |
| ` void` | ` https://developer.android.com/reference/java/util/LinkedHashSet#addLast(E)(E e) ` Adds an element as the last element of this collection (optional operation). If this set already contains the element, it is relocated if necessary so that it is last in encounter order. |
| ` E` | ` https://developer.android.com/reference/java/util/LinkedHashSet#getFirst()() ` Gets the first element of this collection. |
| ` E` | ` https://developer.android.com/reference/java/util/LinkedHashSet#getLast()() ` Gets the last element of this collection. |
| ` static <T> https://developer.android.com/reference/java/util/LinkedHashSet<T>` | ` https://developer.android.com/reference/java/util/LinkedHashSet#newLinkedHashSet(int)(int numElements) ` Creates a new, empty LinkedHashSet suitable for the expected number of elements. |
| ` E` | ` https://developer.android.com/reference/java/util/LinkedHashSet#removeFirst()() ` Removes and returns the first element of this collection (optional operation). |
| ` E` | ` https://developer.android.com/reference/java/util/LinkedHashSet#removeLast()() ` Removes and returns the last element of this collection (optional operation). |
| ` https://developer.android.com/reference/java/util/SequencedSet<E>` | ` https://developer.android.com/reference/java/util/LinkedHashSet#reversed()() ` Returns a reverse-ordered [view](https://developer.android.com/reference/java/util/Collection#view) of this collection. Modifications to the reversed view are permitted and will be propagated to this set. |
| ` https://developer.android.com/reference/java/util/Spliterator<E>` | ` https://developer.android.com/reference/java/util/LinkedHashSet#spliterator()() ` Creates a *[late-binding](https://developer.android.com/reference/java/util/Spliterator#binding)* and *fail-fast* `Spliterator` over the elements in this set. |

| ### Inherited methods |
|---|---|
| From class ` https://developer.android.com/reference/java/util/HashSet ` |---|---| | ` boolean` | ` https://developer.android.com/reference/java/util/HashSet#add(E)(E e) ` Adds the specified element to this set if it is not already present. | | ` void` | ` https://developer.android.com/reference/java/util/HashSet#clear()() ` Removes all of the elements from this set. | | ` https://developer.android.com/reference/java/lang/Object` | ` https://developer.android.com/reference/java/util/HashSet#clone()() ` Returns a shallow copy of this `HashSet` instance: the elements themselves are not cloned. | | ` boolean` | ` https://developer.android.com/reference/java/util/HashSet#contains(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Returns `true` if this set contains the specified element. | | ` boolean` | ` https://developer.android.com/reference/java/util/HashSet#isEmpty()() ` Returns `true` if this set contains no elements. | | ` https://developer.android.com/reference/java/util/Iterator<E>` | ` https://developer.android.com/reference/java/util/HashSet#iterator()() ` Returns an iterator over the elements in this set. | | ` static <T> https://developer.android.com/reference/java/util/HashSet<T>` | ` https://developer.android.com/reference/java/util/HashSet#newHashSet(int)(int numElements) ` Creates a new, empty HashSet suitable for the expected number of elements. | | ` boolean` | ` https://developer.android.com/reference/java/util/HashSet#remove(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Removes the specified element from this set if it is present. | | ` int` | ` https://developer.android.com/reference/java/util/HashSet#size()() ` Returns the number of elements in this set (its cardinality). | | ` https://developer.android.com/reference/java/util/Spliterator<E>` | ` https://developer.android.com/reference/java/util/HashSet#spliterator()() ` Creates a *[late-binding](https://developer.android.com/reference/java/util/Spliterator#binding)* and *fail-fast* `https://developer.android.com/reference/java/util/Spliterator` over the elements in this set. | | ` <T> T[]` | ` https://developer.android.com/reference/java/util/HashSet#toArray(T[])(T[] a) ` Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. | | ` https://developer.android.com/reference/java/lang/Object` | ` https://developer.android.com/reference/java/util/HashSet#toArray()() ` Returns an array containing all of the elements in this collection. | ||
| From class ` https://developer.android.com/reference/java/util/AbstractSet ` |---|---| | ` boolean` | ` https://developer.android.com/reference/java/util/AbstractSet#equals(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Compares the specified object with this set for equality. | | ` int` | ` https://developer.android.com/reference/java/util/AbstractSet#hashCode()() ` Returns the hash code value for this set. | | ` boolean` | ` https://developer.android.com/reference/java/util/AbstractSet#removeAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) ` Removes from this set all of its elements that are contained in the specified collection (optional operation). | ||
| From class ` https://developer.android.com/reference/java/util/AbstractCollection ` |---|---| | ` boolean` | ` https://developer.android.com/reference/java/util/AbstractCollection#add(E)(E e) ` Ensures that this collection contains the specified element (optional operation). | | ` boolean` | ` https://developer.android.com/reference/java/util/AbstractCollection#addAll(java.util.Collection<?%20extends%20E>)(https://developer.android.com/reference/java/util/Collection<? extends E> c) ` Adds all of the elements in the specified collection to this collection (optional operation). | | ` void` | ` https://developer.android.com/reference/java/util/AbstractCollection#clear()() ` Removes all of the elements from this collection (optional operation). | | ` boolean` | ` https://developer.android.com/reference/java/util/AbstractCollection#contains(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Returns `true` if this collection contains the specified element. | | ` boolean` | ` https://developer.android.com/reference/java/util/AbstractCollection#containsAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) ` Returns `true` if this collection contains all of the elements in the specified collection. | | ` boolean` | ` https://developer.android.com/reference/java/util/AbstractCollection#isEmpty()() ` Returns `true` if this collection contains no elements. | | ` abstract https://developer.android.com/reference/java/util/Iterator<E>` | ` https://developer.android.com/reference/java/util/AbstractCollection#iterator()() ` Returns an iterator over the elements contained in this collection. | | ` boolean` | ` https://developer.android.com/reference/java/util/AbstractCollection#remove(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Removes a single instance of the specified element from this collection, if it is present (optional operation). | | ` boolean` | ` https://developer.android.com/reference/java/util/AbstractCollection#removeAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) ` Removes all of this collection's elements that are also contained in the specified collection (optional operation). | | ` boolean` | ` https://developer.android.com/reference/java/util/AbstractCollection#retainAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) ` Retains only the elements in this collection that are contained in the specified collection (optional operation). | | ` abstract int` | ` https://developer.android.com/reference/java/util/AbstractCollection#size()() ` Returns the number of elements in this collection. | | ` <T> T[]` | ` https://developer.android.com/reference/java/util/AbstractCollection#toArray(T[])(T[] a) ` Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. | | ` https://developer.android.com/reference/java/lang/Object` | ` https://developer.android.com/reference/java/util/AbstractCollection#toArray()() ` Returns an array containing all of the elements in this collection. | | ` https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/util/AbstractCollection#toString()() ` Returns a string representation of this collection. | ||
| From class ` https://developer.android.com/reference/java/lang/Object ` |---|---| | ` https://developer.android.com/reference/java/lang/Object` | ` https://developer.android.com/reference/java/lang/Object#clone()() ` Creates and returns a copy of this object. | | ` boolean` | ` https://developer.android.com/reference/java/lang/Object#equals(java.lang.Object)(https://developer.android.com/reference/java/lang/Object obj) ` Indicates whether some other object is "equal to" this one. | | ` void` | ` https://developer.android.com/reference/java/lang/Object#finalize()() ` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. | | ` final https://developer.android.com/reference/java/lang/Class<?>` | ` https://developer.android.com/reference/java/lang/Object#getClass()() ` Returns the runtime class of this `Object`. | | ` int` | ` https://developer.android.com/reference/java/lang/Object#hashCode()() ` Returns a hash code value for the object. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#notify()() ` Wakes up a single thread that is waiting on this object's monitor. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#notifyAll()() ` Wakes up all threads that are waiting on this object's monitor. | | ` https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/lang/Object#toString()() ` Returns a string representation of the object. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait(long,%20int)(long timeoutMillis, int nanos) ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*, or until a certain amount of real time has elapsed. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait(long)(long timeoutMillis) ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*, or until a certain amount of real time has elapsed. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait()() ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*. | ||
| From interface ` https://developer.android.com/reference/java/util/Set ` |---|---| | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Set#add(E)(E e) ` Adds the specified element to this set if it is not already present (optional operation). | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Set#addAll(java.util.Collection<?%20extends%20E>)(https://developer.android.com/reference/java/util/Collection<? extends E> c) ` Adds all of the elements in the specified collection to this set if they're not already present (optional operation). | | ` abstract void` | ` https://developer.android.com/reference/java/util/Set#clear()() ` Removes all of the elements from this set (optional operation). | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Set#contains(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Returns `true` if this set contains the specified element. | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Set#containsAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) ` Returns `true` if this set contains all of the elements of the specified collection. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#copyOf(java.util.Collection<?%20extends%20E>)(https://developer.android.com/reference/java/util/Collection<? extends E> coll) ` Returns an [unmodifiable Set](https://developer.android.com/reference/java/util/LinkedHashSet#unmodifiable) containing the elements of the given Collection. | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Set#equals(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Compares the specified object with this set for equality. | | ` abstract int` | ` https://developer.android.com/reference/java/util/Set#hashCode()() ` Returns the hash code value for this set. | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Set#isEmpty()() ` Returns `true` if this set contains no elements. | | ` abstract https://developer.android.com/reference/java/util/Iterator<E>` | ` https://developer.android.com/reference/java/util/Set#iterator()() ` Returns an iterator over the elements in this set. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E,%20E,%20E)(E e1, E e2, E e3) ` Returns an unmodifiable set containing three elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E,%20E,%20E,%20E,%20E,%20E,%20E,%20E,%20E)(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9) ` Returns an unmodifiable set containing nine elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E,%20E,%20E,%20E,%20E)(E e1, E e2, E e3, E e4, E e5) ` Returns an unmodifiable set containing five elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E,%20E,%20E,%20E,%20E,%20E)(E e1, E e2, E e3, E e4, E e5, E e6) ` Returns an unmodifiable set containing six elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E,%20E,%20E,%20E,%20E,%20E,%20E,%20E)(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8) ` Returns an unmodifiable set containing eight elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E[])(E... elements) ` Returns an unmodifiable set containing an arbitrary number of elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of()() ` Returns an unmodifiable set containing zero elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E,%20E,%20E,%20E,%20E,%20E,%20E,%20E,%20E,%20E)(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10) ` Returns an unmodifiable set containing ten elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E,%20E)(E e1, E e2) ` Returns an unmodifiable set containing two elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E,%20E,%20E,%20E,%20E,%20E,%20E)(E e1, E e2, E e3, E e4, E e5, E e6, E e7) ` Returns an unmodifiable set containing seven elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E,%20E,%20E,%20E)(E e1, E e2, E e3, E e4) ` Returns an unmodifiable set containing four elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E)(E e1) ` Returns an unmodifiable set containing one element. | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Set#remove(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Removes the specified element from this set if it is present (optional operation). | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Set#removeAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) ` Removes from this set all of its elements that are contained in the specified collection (optional operation). | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Set#retainAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) ` Retains only the elements in this set that are contained in the specified collection (optional operation). | | ` abstract int` | ` https://developer.android.com/reference/java/util/Set#size()() ` Returns the number of elements in this set (its cardinality). | | ` default https://developer.android.com/reference/java/util/Spliterator<E>` | ` https://developer.android.com/reference/java/util/Set#spliterator()() ` Creates a `Spliterator` over the elements in this set. | | ` abstract https://developer.android.com/reference/java/lang/Object` | ` https://developer.android.com/reference/java/util/Set#toArray()() ` Returns an array containing all of the elements in this set. | | ` abstract <T> T[]` | ` https://developer.android.com/reference/java/util/Set#toArray(T[])(T[] a) ` Returns an array containing all of the elements in this set; the runtime type of the returned array is that of the specified array. | ||
| From interface ` https://developer.android.com/reference/java/util/Collection ` |---|---| | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Collection#add(E)(E e) ` Ensures that this collection contains the specified element (optional operation). | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Collection#addAll(java.util.Collection<?%20extends%20E>)(https://developer.android.com/reference/java/util/Collection<? extends E> c) ` Adds all of the elements in the specified collection to this collection (optional operation). | | ` abstract void` | ` https://developer.android.com/reference/java/util/Collection#clear()() ` Removes all of the elements from this collection (optional operation). | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Collection#contains(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Returns `true` if this collection contains the specified element. | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Collection#containsAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) ` Returns `true` if this collection contains all of the elements in the specified collection. | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Collection#equals(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Compares the specified object with this collection for equality. | | ` abstract int` | ` https://developer.android.com/reference/java/util/Collection#hashCode()() ` Returns the hash code value for this collection. | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Collection#isEmpty()() ` Returns `true` if this collection contains no elements. | | ` abstract https://developer.android.com/reference/java/util/Iterator<E>` | ` https://developer.android.com/reference/java/util/Collection#iterator()() ` Returns an iterator over the elements in this collection. | | ` default https://developer.android.com/reference/java/util/stream/Stream<E>` | ` https://developer.android.com/reference/java/util/Collection#parallelStream()() ` Returns a possibly parallel `Stream` with this collection as its source. | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Collection#remove(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Removes a single instance of the specified element from this collection, if it is present (optional operation). | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Collection#removeAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) ` Removes all of this collection's elements that are also contained in the specified collection (optional operation). | | ` default boolean` | ` https://developer.android.com/reference/java/util/Collection#removeIf(java.util.function.Predicate<?%20super%20E>)(https://developer.android.com/reference/java/util/function/Predicate<? super E> filter) ` Removes all of the elements of this collection that satisfy the given predicate (optional operation). | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Collection#retainAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) ` Retains only the elements in this collection that are contained in the specified collection (optional operation). | | ` abstract int` | ` https://developer.android.com/reference/java/util/Collection#size()() ` Returns the number of elements in this collection. | | ` default https://developer.android.com/reference/java/util/Spliterator<E>` | ` https://developer.android.com/reference/java/util/Collection#spliterator()() ` Creates a `https://developer.android.com/reference/java/util/Spliterator` over the elements in this collection. | | ` default https://developer.android.com/reference/java/util/stream/Stream<E>` | ` https://developer.android.com/reference/java/util/Collection#stream()() ` Returns a sequential `Stream` with this collection as its source. | | ` abstract <T> T[]` | ` https://developer.android.com/reference/java/util/Collection#toArray(T[])(T[] a) ` Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. | | ` abstract https://developer.android.com/reference/java/lang/Object` | ` https://developer.android.com/reference/java/util/Collection#toArray()() ` Returns an array containing all of the elements in this collection. | | ` default <T> T[]` | ` https://developer.android.com/reference/java/util/Collection#toArray(java.util.function.IntFunction<T[]>)(https://developer.android.com/reference/java/util/function/IntFunction<T[]> generator) ` Returns an array containing all of the elements in this collection, using the provided `generator` function to allocate the returned array. | ||
| From interface ` https://developer.android.com/reference/java/util/SequencedSet ` |---|---| | ` abstract https://developer.android.com/reference/java/util/SequencedSet<E>` | ` https://developer.android.com/reference/java/util/SequencedSet#reversed()() ` Returns a reverse-ordered [view](https://developer.android.com/reference/java/util/Collection#view) of this collection. | ||
| From interface ` https://developer.android.com/reference/java/lang/Iterable ` |---|---| | ` default void` | ` https://developer.android.com/reference/java/lang/Iterable#forEach(java.util.function.Consumer<?%20super%20T>)(https://developer.android.com/reference/java/util/function/Consumer<? super T> action) ` Performs the given action for each element of the `Iterable` until all elements have been processed or the action throws an exception. | | ` abstract https://developer.android.com/reference/java/util/Iterator<E>` | ` https://developer.android.com/reference/java/lang/Iterable#iterator()() ` Returns an iterator over elements of type `T`. | | ` default https://developer.android.com/reference/java/util/Spliterator<E>` | ` https://developer.android.com/reference/java/lang/Iterable#spliterator()() ` Creates a `https://developer.android.com/reference/java/util/Spliterator` over the elements described by this `Iterable`. | ||
| From interface ` https://developer.android.com/reference/java/util/SequencedCollection ` |---|---| | ` default void` | ` https://developer.android.com/reference/java/util/SequencedCollection#addFirst(E)(E e) ` Adds an element as the first element of this collection (optional operation). | | ` default void` | ` https://developer.android.com/reference/java/util/SequencedCollection#addLast(E)(E e) ` Adds an element as the last element of this collection (optional operation). | | ` default E` | ` https://developer.android.com/reference/java/util/SequencedCollection#getFirst()() ` Gets the first element of this collection. | | ` default E` | ` https://developer.android.com/reference/java/util/SequencedCollection#getLast()() ` Gets the last element of this collection. | | ` default E` | ` https://developer.android.com/reference/java/util/SequencedCollection#removeFirst()() ` Removes and returns the first element of this collection (optional operation). | | ` default E` | ` https://developer.android.com/reference/java/util/SequencedCollection#removeLast()() ` Removes and returns the last element of this collection (optional operation). | | ` abstract https://developer.android.com/reference/java/util/SequencedCollection<E>` | ` https://developer.android.com/reference/java/util/SequencedCollection#reversed()() ` Returns a reverse-ordered [view](https://developer.android.com/reference/java/util/Collection#view) of this collection. | ||

## Public constructors

### LinkedHashSet

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public LinkedHashSet ()
```

Constructs a new, empty linked hash set with the default initial
capacity (16) and load factor (0.75).

<br />

### LinkedHashSet

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public LinkedHashSet (int initialCapacity)
```

Constructs a new, empty linked hash set with the specified initial
capacity and the default load factor (0.75).

<br />

##### API Note:

- To create a `LinkedHashSet` with an initial capacity that accommodates an expected number of elements, use `https://developer.android.com/reference/java/util/LinkedHashSet#newLinkedHashSet(int)`.

| Parameters ||
|---|---|
| `initialCapacity` | `int`: the initial capacity of the LinkedHashSet <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if the initial capacity is less than zero |

### LinkedHashSet

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public LinkedHashSet (int initialCapacity, 
                float loadFactor)
```

Constructs a new, empty linked hash set with the specified initial
capacity and load factor.

<br />

##### API Note:

- To create a `LinkedHashSet` with an initial capacity that accommodates an expected number of elements, use `https://developer.android.com/reference/java/util/LinkedHashSet#newLinkedHashSet(int)`.

| Parameters ||
|---|---|
| `initialCapacity` | `int`: the initial capacity of the linked hash set <br /> |
| `loadFactor` | `float`: the load factor of the linked hash set <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if the initial capacity is less than zero, or if the load factor is nonpositive |

### LinkedHashSet

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public LinkedHashSet (Collection<? extends E> c)
```

Constructs a new linked hash set with the same elements as the
specified collection. The linked hash set is created with an initial
capacity sufficient to hold the elements in the specified collection
and the default load factor (0.75).

<br />

| Parameters ||
|---|---|
| `c` | `Collection`: the collection whose elements are to be placed into this set <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the specified collection is null |

## Public methods

### addFirst

Added in [API level 35](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public void addFirst (E e)
```

Adds an element as the first element of this collection (optional operation).
After this operation completes normally, the given element will be a member of
this collection, and it will be the first element in encounter order.


If this set already contains the element, it is relocated if necessary so that it is
first in encounter order.

<br />

| Parameters ||
|---|---|
| `e` | `E`: the element to be added <br /> |

### addLast

Added in [API level 35](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public void addLast (E e)
```

Adds an element as the last element of this collection (optional operation).
After this operation completes normally, the given element will be a member of
this collection, and it will be the last element in encounter order.


If this set already contains the element, it is relocated if necessary so that it is
last in encounter order.

<br />

| Parameters ||
|---|---|
| `e` | `E`: the element to be added. <br /> |

### getFirst

Added in [API level 35](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public E getFirst ()
```

Gets the first element of this collection.

<br />

| Returns ||
|---|---|
| `E` | the retrieved element <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/util/NoSuchElementException` |   |

### getLast

Added in [API level 35](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public E getLast ()
```

Gets the last element of this collection.

<br />

| Returns ||
|---|---|
| `E` | the retrieved element <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/util/NoSuchElementException` |   |

### newLinkedHashSet

Added in [API level 35](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public static LinkedHashSet<T> newLinkedHashSet (int numElements)
```

Creates a new, empty LinkedHashSet suitable for the expected number of elements.
The returned set uses the default load factor of 0.75, and its initial capacity is
generally large enough so that the expected number of elements can be added
without resizing the set.

<br />

| Parameters ||
|---|---|
| `numElements` | `int`: the expected number of elements <br /> |

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/LinkedHashSet<T>` | the newly created set <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if numElements is negative |

### removeFirst

Added in [API level 35](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public E removeFirst ()
```

Removes and returns the first element of this collection (optional operation).

<br />

| Returns ||
|---|---|
| `E` | the removed element <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/util/NoSuchElementException` |   |

### removeLast

Added in [API level 35](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public E removeLast ()
```

Removes and returns the last element of this collection (optional operation).

<br />

| Returns ||
|---|---|
| `E` | the removed element <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/util/NoSuchElementException` |   |

### reversed

Added in [API level 35](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public SequencedSet<E> reversed ()
```

Returns a reverse-ordered [view](https://developer.android.com/reference/java/util/Collection#view) of this collection.
The encounter order of elements in the returned view is the inverse of the encounter
order of elements in this collection. The reverse ordering affects all order-sensitive
operations, including those on the view collections of the returned view. If the collection
implementation permits modifications to this view, the modifications "write through" to the
underlying collection. Changes to the underlying collection might or might not be visible
in this reversed view, depending upon the implementation.


Modifications to the reversed view are permitted and will be propagated to this set.
In addition, modifications to this set will be visible in the reversed view.

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/SequencedSet<E>` | a reverse-ordered view of this collection, as a `SequencedSet` <br /> |

### spliterator

Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public Spliterator<E> spliterator ()
```

Creates a *[late-binding](https://developer.android.com/reference/java/util/Spliterator#binding)*
and *fail-fast* `Spliterator` over the elements in this set.

The `Spliterator` reports `https://developer.android.com/reference/java/util/Spliterator#SIZED`,
`https://developer.android.com/reference/java/util/Spliterator#DISTINCT`, and `ORDERED`. Implementations
should document the reporting of additional characteristic values.

<br />

##### Implementation Note:

- The implementation creates a *[late-binding](https://developer.android.com/reference/java/util/Spliterator#binding)* spliterator from the set's `Iterator`. The spliterator inherits the *fail-fast* properties of the set's iterator. The created `Spliterator` additionally reports `https://developer.android.com/reference/java/util/Spliterator#SUBSIZED`.

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/Spliterator<E>` | a `Spliterator` over the elements in this set <br /> |