org.openjdk.jmc.common.collection

Class FastAccessNumberMap<T>

java.lang.Object

org.openjdk.jmc.common.collection.FastAccessNumberMap<T>

Type Parameters:

T - type of objects to store in this map

All Implemented Interfaces:

Iterable<T>

public class FastAccessNumberMap<T>
extends Object
implements Iterable<T>

A map from long to T. Gives O(1) access to indexes that are between 0 and pageSize*maxPageCount at the cost of high memory use. Values are kept in dynamically allocated pages, each of a fixed size.

It can be thought of as a big array that is split up into pages of a fixed size. This is useful if you want to use a sparse set of indexes since you don't have to allocate the full array immediately. If you are going to fill all indexes then it is more practical to use a normal array or list.

If you try to access an index outside of the max page count then an overflow hash map is used as a fallback mechanism. In that case access will be slower than O(1).

Constructor Summary

Constructors

Constructor and Description
FastAccessNumberMap() Constructs a map with O(1) access up to index 5000.
FastAccessNumberMap(int pageSize, int maxPageCount) Constructs a map with O(1) access up to index pageSize*maxPageCount.

Method Summary

Modifier and Type	Method and Description
T	get(long index) Get the value at an index.
Iterator<T>	iterator()
void	put(long index, T value) Store a value at an index.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Constructor Detail

FastAccessNumberMap

public FastAccessNumberMap()

Constructs a map with O(1) access up to index 5000.

FastAccessNumberMap

public FastAccessNumberMap(int pageSize,
                           int maxPageCount)

Constructs a map with O(1) access up to index pageSize*maxPageCount.

Parameters:

pageSize - page size

maxPageCount - max page count

Method Detail

get

public T get(long index)

Get the value at an index.

Parameters:

index - value index

Returns:

value at index

put

public void put(long index,
                T value)

Store a value at an index.

Parameters:

index - value index

value - value to store

iterator

public Iterator<T> iterator()

Specified by:

iterator in interface Iterable<T>