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Summary: Ctors | Methods | Inherited Methods

# SparseLongArray

`public class SparseLongArray`
`extends Object` `implements Cloneable`

java.lang.Object
↳ | android.util.SparseLongArray

SparseLongArrays map integers to longs. Unlike a normal array of longs, there can be gaps in the indices. It is intended to be more memory efficient than using a HashMap to map Integers to Longs, both because it avoids auto-boxing keys and values and its data structure doesn't rely on an extra entry object for each mapping.

Note that this container keeps its mappings in an array data structure, using a binary search to find keys. The implementation is not intended to be appropriate for data structures that may contain large numbers of items. It is generally slower than a traditional HashMap, since lookups require a binary search and adds and removes require inserting and deleting entries in the array. For containers holding up to hundreds of items, the performance difference is not significant, less than 50%.

It is possible to iterate over the items in this container using `keyAt(int)` and `valueAt(int)`. Iterating over the keys using `keyAt(int)` with ascending values of the index will return the keys in ascending order, or the values corresponding to the keys in ascending order in the case of `valueAt(int)`.

## Summary

### Public constructors
`SparseLongArray()` Creates a new SparseLongArray containing no mappings.
`SparseLongArray(int initialCapacity)` Creates a new SparseLongArray containing no mappings that will not require any additional memory allocation to store the specified number of mappings.

### Public methods
`void` | `append(int key, long value)` Puts a key/value pair into the array, optimizing for the case where the key is greater than all existing keys in the array.
`void` | `clear()` Removes all key-value mappings from this SparseLongArray.
`SparseLongArray` | `clone()` Creates and returns a copy of this object.
`void` | `delete(int key)` Removes the mapping from the specified key, if there was any.
`long` | `get(int key)` Gets the long mapped from the specified key, or `0` if no such mapping has been made.
`long` | `get(int key, long valueIfKeyNotFound)` Gets the long mapped from the specified key, or the specified value if no such mapping has been made.
`int` | `indexOfKey(int key)` Returns the index for which `keyAt(int)` would return the specified key, or a negative number if the specified key is not mapped.
`int` | `indexOfValue(long value)` Returns an index for which `valueAt(int)` would return the specified key, or a negative number if no keys map to the specified value.
`int` | `keyAt(int index)` Given an index in the range `0...size()-1`, returns the key from the `index`th key-value mapping that this SparseLongArray stores.
`void` | `put(int key, long value)` Adds a mapping from the specified key to the specified value, replacing the previous mapping from the specified key if there was one.
`void` | `removeAt(int index)` Removes the mapping at the given index.
`int` | `size()` Returns the number of key-value mappings that this SparseLongArray currently stores.
`String` | `toString()` Returns a string representation of the object. This implementation composes a string by iterating over its mappings.
`long` | `valueAt(int index)` Given an index in the range `0...size()-1`, returns the value from the `index`th key-value mapping that this SparseLongArray stores.

### Inherited methods
From class `java.lang.Object`
`Object` | `clone()` Creates and returns a copy of this object.
`boolean` | `equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void` | `finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>` | `getClass()` Returns the runtime class of this `Object`.
`int` | `hashCode()` Returns a hash code value for the object.
`final void` | `notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void` | `notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String` | `toString()` Returns a string representation of the object.
`final void` | `wait(long timeout, int nanos)` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
`final void` | `wait(long timeout)` Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.
`final void` | `wait()` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.

## Public constructors

### SparseLongArray

    public SparseLongArray ()

Creates a new SparseLongArray containing no mappings.

### SparseLongArray

    public SparseLongArray (int initialCapacity)

Creates a new SparseLongArray containing no mappings that will not require any additional memory allocation to store the specified number of mappings. If you supply an initial capacity of 0, the sparse array will be initialized with a light-weight representation not requiring any additional array allocations.

Parameters
`initialCapacity` | `int`

## Public methods

### append

    public void append (int key,
                    long value)

Puts a key/value pair into the array, optimizing for the case where the key is greater than all existing keys in the array.

Parameters
`key` | `int`
`value` | `long`

### clear

    public void clear ()

Removes all key-value mappings from this SparseLongArray.

### clone

    public SparseLongArray clone ()

Creates and returns a copy of this object. The precise meaning of "copy" may depend on the class of the object. The general intent is that, for any object `x`, the expression:

>      x.clone() != x

will be true, and that the expression:

>      x.clone().getClass() == x.getClass()

will be `true`, but these are not absolute requirements. While it is typically the case that:

>      x.clone().equals(x)

will be `true`, this is not an absolute requirement.

By convention, the returned object should be obtained by calling `super.clone`. If a class and all of its superclasses (except `Object`) obey this convention, it will be the case that `x.clone().getClass() == x.getClass()`.

By convention, the object returned by this method should be independent of this object (which is being cloned). To achieve this independence, it may be necessary to modify one or more fields of the object returned by `super.clone` before returning it. Typically, this means copying any mutable objects that comprise the internal "deep structure" of the object being cloned and replacing the references to these objects with references to the copies. If a class contains only primitive fields or references to immutable objects, then it is usually the case that no fields in the object returned by `super.clone` need to be modified.

The method `clone` for class `Object` performs a specific cloning operation. First, if the class of this object does not implement the interface `Cloneable`, then a `CloneNotSupportedException` is thrown. Note that all arrays are considered to implement the interface `Cloneable` and that the return type of the `clone` method of an array type `T[]` is `T[]` where T is any reference or primitive type. Otherwise, this method creates a new instance of the class of this object and initializes all its fields with exactly the contents of the corresponding fields of this object, as if by assignment; the contents of the fields are not themselves cloned. Thus, this method performs a "shallow copy" of this object, not a "deep copy" operation.

The class `Object` does not itself implement the interface `Cloneable`, so calling the `clone` method on an object whose class is `Object` will result in throwing an exception at run time.

Returns
`SparseLongArray` | a clone of this instance.

### delete

    public void delete (int key)

Removes the mapping from the specified key, if there was any.

Parameters
`key` | `int`

### get

    public long get (int key)

Gets the long mapped from the specified key, or `0` if no such mapping has been made.

Parameters
`key` | `int`

Returns
`long` |

### get

    public long get (int key,
                    long valueIfKeyNotFound)

Gets the long mapped from the specified key, or the specified value if no such mapping has been made.

Parameters
`key` | `int`
`valueIfKeyNotFound` | `long`

Returns
`long` |

### indexOfKey

    public int indexOfKey (int key)

Returns the index for which `keyAt(int)` would return the specified key, or a negative number if the specified key is not mapped.

Parameters
`key` | `int`

Returns
`int` |

### indexOfValue

    public int indexOfValue (long value)

Returns an index for which `valueAt(int)` would return the specified key, or a negative number if no keys map to the specified value. Beware that this is a linear search, unlike lookups by key, and that multiple keys can map to the same value and this will find only one of them.

Parameters
`value` | `long`

Returns
`int` |

### keyAt

    public int keyAt (int index)

Given an index in the range `0...size()-1`, returns the key from the `index`th key-value mapping that this SparseLongArray stores.

The keys corresponding to indices in ascending order are guaranteed to be in ascending order, e.g., `keyAt(0)` will return the smallest key and `keyAt(size()-1)` will return the largest key.

For indices outside of the range `0...size()-1`, the behavior is undefined for apps targeting `Build.VERSION_CODES.P` and earlier, and an `ArrayIndexOutOfBoundsException` is thrown for apps targeting `Build.VERSION_CODES.Q` and later.

Parameters
`index` | `int`

Returns
`int` |

### put

    public void put (int key,
                    long value)

Adds a mapping from the specified key to the specified value, replacing the previous mapping from the specified key if there was one.

Parameters
`key` | `int`
`value` | `long`

### removeAt

    public void removeAt (int index)

Removes the mapping at the given index.

Parameters
`index` | `int`

### size

    public int size ()

Returns the number of key-value mappings that this SparseLongArray currently stores.

Returns
`int` |

### toString

    public String toString ()

Returns a string representation of the object. In general, the `toString` method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.

The `toString` method for class `Object` returns a string consisting of the name of the class of which the object is an instance, the at-sign character ``@`', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:

>      getClass().getName() + '@' + Integer.toHexString(hashCode())

This implementation composes a string by iterating over its mappings.

Returns
`String` | a string representation of the object.

### valueAt

    public long valueAt (int index)

Given an index in the range `0...size()-1`, returns the value from the `index`th key-value mapping that this SparseLongArray stores.

The values corresponding to indices in ascending order are guaranteed to be associated with keys in ascending order, e.g., `valueAt(0)` will return the value associated with the smallest key and `valueAt(size()-1)` will return the value associated with the largest key.

For indices outside of the range `0...size()-1`, the behavior is undefined for apps targeting `Build.VERSION_CODES.P` and earlier, and an `ArrayIndexOutOfBoundsException` is thrown for apps targeting `Build.VERSION_CODES.Q` and later.

Parameters
`index` | `int`

Returns
`long` |

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