Package 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 Details

    • FastAccessNumberMap

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

    • FastAccessNumberMap

      public FastAccessNumberMap(int expectedSize)
      Constructs a map with O(1) access up to index expectedSize.
      Parameters:
      expectedSize - - the maximum number of elements expected to be inserted into the map before overflowing to slower storage.

    • 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 Details

    • 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>