Package org.apache.lucene.util

Class SentinelIntSet

java.lang.Object
org.apache.lucene.util.SentinelIntSet
public class SentinelIntSet extends Object
A native int hash-based set where one value is reserved to mean "EMPTY" internally. The space overhead is fairly low as there is only one power-of-two sized int[] to hold the values. The set is re-hashed when adding a value that would make it >= 75% full. Consider extending and over-riding hash(int) if the values might be poor hash keys; Lucene docids should be fine. The internal fields are exposed publicly to enable more efficient use at the expense of better O-O principles.

To iterate over the integers held in this set, simply use code like this: 

 SentinelIntSet set = ...
 for (int v : set.keys) {
   if (v == set.emptyVal)
     continue;
   //use v...
 }

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    int
    count
     
    final int
    emptyVal
     
    int[]
    keys
    A power-of-2 over-sized array holding the integers in the set along with empty values.
    int
    rehashCount
    the count at which a rehash should be done

  • Constructor Summary

    Constructors
    Constructor
    Description
    SentinelIntSet(int size, int emptyVal)
     

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    clear()
     
    boolean
    exists(int key)
    Does this set contain the specified integer?
    int
    find(int key)
    (internal) Returns the slot for this key, or -slot-1 if not found
    int
    getSlot(int key)
    (internal) Returns the slot for this key
    int
    hash(int key)
    (internal) Return the hash for the key.
    int
    put(int key)
    Puts this integer (key) in the set, and returns the slot index it was added to.
    void
    rehash()
    (internal) Rehashes by doubling int[] key and filling with the old values.
    int
    size()
    The number of integers in this set.

    Methods inherited from class java.lang.Object

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

  • Field Details

    • keys

      public int[] keys
      A power-of-2 over-sized array holding the integers in the set along with empty values.

    • count

      public int count

    • emptyVal

      public final int emptyVal

    • rehashCount

      public int rehashCount
      the count at which a rehash should be done

  • Constructor Details

    • SentinelIntSet

      public SentinelIntSet(int size, int emptyVal)
      Parameters:
      size - The minimum number of elements this set should be able to hold without rehashing (i.e. the slots are guaranteed not to change)
      emptyVal - The integer value to use for EMPTY

  • Method Details

    • clear

      public void clear()

    • hash

      public int hash(int key)
      (internal) Return the hash for the key. The default implementation just returns the key, which is not appropriate for general purpose use.

    • size

      public int size()
      The number of integers in this set.

    • getSlot

      public int getSlot(int key)
      (internal) Returns the slot for this key

    • find

      public int find(int key)
      (internal) Returns the slot for this key, or -slot-1 if not found

    • exists

      public boolean exists(int key)
      Does this set contain the specified integer?

    • put

      public int put(int key)
      Puts this integer (key) in the set, and returns the slot index it was added to. It rehashes if adding it would make the set more than 75% full.

    • rehash

      public void rehash()
      (internal) Rehashes by doubling int[] key and filling with the old values.