public class PrimeFinder
extends java.lang.Object
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.
This class has been adapted from the corresponding class in the COLT library for scientfic computing.Modifier and Type | Field and Description |
---|---|
static int |
largestPrime
The largest prime this class can generate; currently equal to
Integer.MAX_VALUE.
|
Modifier | Constructor and Description |
---|---|
protected |
PrimeFinder()
Makes this class non instantiable, but still let's others inherit from
it.
|
Modifier and Type | Method and Description |
---|---|
static int |
nextPrime(int desiredCapacity)
Returns a prime number which is
>= desiredCapacity and
very close to desiredCapacity (within 11% if
desiredCapacity >= 1000 ). |
public static final int largestPrime
protected PrimeFinder()
public static int nextPrime(int desiredCapacity)
>= desiredCapacity
and
very close to desiredCapacity
(within 11% if
desiredCapacity >= 1000
).desiredCapacity
- the capacity desired by the user.Copyright ? 2013 Regents of the University of California