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## 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`).

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### largestPrime

    public static final int largestPrime

  The largest prime this class can generate; currently equal to `Integer.MAX_VALUE`.

  See Also:
    Constant Field Values

Method Detail

### 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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