ScatterSet
Known direct subclasses
MutableScatterSet

MutableScatterSet is a container with a MutableSet-like interface based on a flat hash table implementation.

ScatterSet is a container with a Set-like interface based on a flat hash table implementation. The underlying implementation is designed to avoid all allocations on insertion, removal, retrieval, and iteration. Allocations may still happen on insertion when the underlying storage needs to grow to accommodate newly added elements to the set.

This implementation makes no guarantee as to the order of the elements, nor does it make guarantees that the order remains constant over time. If the order of the elements must be preserved, please refer to OrderedScatterSet.

Though ScatterSet offers a read-only interface, it is always backed by a MutableScatterSet. Read operations alone are thread-safe. However, any mutations done through the backing MutableScatterSet while reading on another thread are not safe and the developer must protect the set from such changes during read operations.

Note: when a Set is absolutely necessary, you can use the method asSet to create a thin wrapper around a ScatterSet. Please refer to asSet for more details and caveats.

See also
MutableScatterSet

Summary

Protected constructors
<E : Any?> ScatterSet()
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Public functions
inline Boolean
all(predicate: (element) -> Boolean)

Returns true if all elements match the given predicate.
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Boolean
any()

Returns true if this set has at least one element.
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inline Boolean
any(predicate: (element) -> Boolean)

Returns true if at least one element matches the given predicate.
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Set<E>

Wraps this ScatterSet with a Set interface.
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operator Boolean
contains(element: E)

Returns true if the specified element is present in this hash set, false otherwise.
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@IntRange(from = 0) Int

Returns the number of elements in this set.
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inline @IntRange(from = 0) Int
count(predicate: (element) -> Boolean)

Returns the number of elements matching the given predicate.
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open operator Boolean
equals(other: Any?)

Compares the specified object other with this hash set for equality.
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E

Returns the first element in the collection.
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inline E
first(predicate: (element) -> Boolean)

Returns the first element in the collection for which predicate returns true
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inline E?
firstOrNull(predicate: (element) -> Boolean)

Returns the first element in the collection for which predicate returns true or null if there are no elements that match predicate.
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inline Unit
forEach(block: (element) -> Unit)

Iterates over every element stored in this set by invoking the specified block lambda.
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open Int

Returns the hash code value for this set.
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Boolean

Indicates whether this set is empty.
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Boolean

Returns true if this set is not empty.
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String
joinToString(
    separator: CharSequence,
    prefix: CharSequence,
    postfix: CharSequence,
    limit: Int,
    truncated: CharSequence,
    transform: ((E) -> CharSequence)?
)

Creates a String from the elements separated by separator and using prefix before and postfix after, if supplied.
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Boolean

Returns true if this set has no elements.
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open String

Returns a string representation of this set.
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Public properties
Int

Returns the number of elements that can be stored in this set without requiring internal storage reallocation.
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Int

Returns the number of elements in this set.
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Protected constructors

ScatterSet

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protected <E : Any?> ScatterSet()

Public functions

all

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Added in 1.4.0
inline fun all(predicate: (element) -> Boolean): Boolean

Returns true if all elements match the given predicate. If there are no elements in the set, true is returned.

Parameters
predicate: (element) -> Boolean

called for elements in the set to determine if it returns return true for all elements.

any

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Added in 1.4.0
fun any(): Boolean

Returns true if this set has at least one element.

any

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Added in 1.4.0
inline fun any(predicate: (element) -> Boolean): Boolean

Returns true if at least one element matches the given predicate.

Parameters
predicate: (element) -> Boolean

called for elements in the set to determine if it returns true for any elements.

asSet

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Added in 1.4.0
fun asSet(): Set<E>

Wraps this ScatterSet with a Set interface. The Set is backed by the ScatterSet, so changes to the ScatterSet are reflected in the Set. If the ScatterSet is modified while an iteration over the Set is in progress, the results of the iteration are undefined.

Note: while this method is useful to use this ScatterSet with APIs accepting Set interfaces, it is less efficient to do so than to use ScatterSet's APIs directly. While the Set implementation returned by this method tries to be as efficient as possible, the semantics of Set may require the allocation of temporary objects for access and iteration.

contains

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Added in 1.4.0
operator fun contains(element: E): Boolean

Returns true if the specified element is present in this hash set, false otherwise.

Parameters
element: E

The element to look for in this set

count

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Added in 1.4.0
fun count(): @IntRange(from = 0) Int

Returns the number of elements in this set.

count

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Added in 1.4.0
inline fun count(predicate: (element) -> Boolean): @IntRange(from = 0) Int

Returns the number of elements matching the given predicate.

Parameters
predicate: (element) -> Boolean

Called for all elements in the set to count the number for which it returns true.

equals

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open operator fun equals(other: Any?): Boolean

Compares the specified object other with this hash set for equality. The two objects are considered equal if other:

  • Is a ScatterSet

  • Has the same size as this set

  • Contains elements equal to this set's elements

first

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Added in 1.4.0
fun first(): E

Returns the first element in the collection.

Throws
kotlin.NoSuchElementException

if the collection is empty

first

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Added in 1.4.0
inline fun first(predicate: (element) -> Boolean): E

Returns the first element in the collection for which predicate returns true

Parameters
predicate: (element) -> Boolean

called with each element until it returns true.
Returns
E

The element for which predicate returns true.
Throws
kotlin.NoSuchElementException

if predicate returns false for all elements or the collection is empty.

firstOrNull

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Added in 1.4.0
inline fun firstOrNull(predicate: (element) -> Boolean): E?

Returns the first element in the collection for which predicate returns true or null if there are no elements that match predicate.

Parameters
predicate: (element) -> Boolean

called with each element until it returns true.
Returns
E?

The element for which predicate returns true or null if there are no elements in the set or predicate returned false for every element in the set.

forEach

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Added in 1.4.0
inline fun forEach(block: (element) -> Unit): Unit

Iterates over every element stored in this set by invoking the specified block lambda. It is safe to remove the element passed to block during iteration.

Parameters
block: (element) -> Unit

called with each element in the set

hashCode

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open fun hashCode(): Int

Returns the hash code value for this set. The hash code of a set is based on the sum of the hash codes of the elements in the set, where the hash code of a null element is defined to be zero.

isEmpty

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Added in 1.4.0
fun isEmpty(): Boolean

Indicates whether this set is empty.

isNotEmpty

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Added in 1.4.0
fun isNotEmpty(): Boolean

Returns true if this set is not empty.

joinToString

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fun joinToString(
    separator: CharSequence = ", ",
    prefix: CharSequence = "",
    postfix: CharSequence = "",
    limit: Int = -1,
    truncated: CharSequence = "...",
    transform: ((E) -> CharSequence)? = null
): String

Creates a String from the elements separated by separator and using prefix before and postfix after, if supplied.

When a non-negative value of limit is provided, a maximum of limit items are used to generate the string. If the collection holds more than limit items, the string is terminated with truncated.

transform may be supplied to convert each element to a custom String.

none

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Added in 1.4.0
fun none(): Boolean

Returns true if this set has no elements.

toString

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open fun toString(): String

Returns a string representation of this set. The set is denoted in the string by the []. Each element is separated by , .

Public properties

capacity

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Added in 1.4.0
val capacity: Int

Returns the number of elements that can be stored in this set without requiring internal storage reallocation.

size

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Added in 1.4.0
val size: Int

Returns the number of elements in this set.