cern.colt.map
Class PrimeFinder
java.lang.Object
|
+--cern.colt.map.PrimeFinder
- public class PrimeFinder
- extends Object
Not of interest for users; only for implementors of hashtables.
Used to keep hash table capacities prime numbers.
Choosing prime numbers as hash table capacities is a good idea to keep them working fast,
particularly under hash table expansions.
However, JDK 1.2, JGL 3.1 and many other toolkits do nothing to keep capacities prime.
This class provides efficient means to choose prime capacities.
Choosing a prime is O(log 300) (binary search in a list of 300 int's).
Memory requirements: 1 KB static memory.
- Version:
- 1.0, 09/24/99
Field Summary |
static int |
largestPrime
The largest prime this class can generate; currently equal to Integer.MAX_VALUE. |
Method Summary |
static int |
nextPrime(int desiredCapacity)
Returns a prime number which is >= desiredCapacity and very close to desiredCapacity (within 11% if desiredCapacity >= 1000 ). |
largestPrime
public static final int largestPrime
- The largest prime this class can generate; currently equal to Integer.MAX_VALUE.
nextPrime
public static int nextPrime(int desiredCapacity)
- Returns a prime number which is
>= desiredCapacity
and very close to desiredCapacity
(within 11% if desiredCapacity >= 1000
).
- Parameters:
desiredCapacity
- the capacity desired by the user.- Returns:
- the capacity which should be used for a hashtable.
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