1 /*
   2  * Copyright (c) 2013 Oracle and/or its affiliates. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  *
   8  *   - Redistributions of source code must retain the above copyright
   9  *     notice, this list of conditions and the following disclaimer.
  10  *
  11  *   - Redistributions in binary form must reproduce the above copyright
  12  *     notice, this list of conditions and the following disclaimer in the
  13  *     documentation and/or other materials provided with the distribution.
  14  *
  15  *   - Neither the name of Oracle nor the names of its
  16  *     contributors may be used to endorse or promote products derived
  17  *     from this software without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
  20  * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  24  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  25  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  26  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  27  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  28  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  29  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  30  */
  31 
  32 /*
  33  * This source code is provided to illustrate the usage of a given feature
  34  * or technique and has been deliberately simplified. Additional steps
  35  * required for a production-quality application, such as security checks,
  36  * input validation and proper error handling, might not be present in
  37  * this sample code.
  38  */
  39 package stream.parallel;
  40 
  41 import java.math.BigInteger;
  42 import java.util.Random;
  43 import java.util.stream.LongStream;
  44 
  45 /**
  46  * This demo shows how to use the parallel mode to find several number of
  47  * unknown length�prime number. The process easily use new Random.LongStream
  48  * generates a desired length stream. Following with filter operation. Here
  49  * input length is desirable long stream length instead of number of prime
  50  * number.
  51  *
  52  * @author tyan
  53  */
  54 public class RandomPrimeNumber {
  55     /**
  56      * By default we only calculate at most 64 numbers once..
  57      */
  58     private final static long RANGE_SIZE = 1 << 6;
  59 
  60     /**
  61      * Try to get length from command line. Use the length to create random long
  62      * stream, that integer's digit is length.
  63      *
  64      * @param args This has to be a 1-element or 2-elements array, The first
  65      * element must be a positive number, which equals to length of generated
  66      * prime number stream. Second element is optional, it will be used as how
  67      * many prime number that will be generated if it's set.
  68      */
  69     public static void main(String[] args) {
  70         if (args.length != 1 && args.length != 2) {
  71             usage();
  72             return;
  73         }
  74         try {
  75             int length = Integer.parseInt(args[0]);
  76             if (length > 16) {
  77                 System.out.println("Can calculate maximun only l6 digits "
  78                         + "prime number");
  79                 return;
  80             }
  81             long numberOfPrime = RANGE_SIZE;
  82             if (args.length == 2) {
  83                 numberOfPrime = Long.parseLong(args[1]);
  84             }
  85             long minNDigit = BigInteger.valueOf(10L).pow(length - 1).longValue();
  86             long maxNDigit = BigInteger.valueOf(10L).pow(length).longValue();
  87 
  88             new Random(System.currentTimeMillis()).
  89                     longs(numberOfPrime, minNDigit, maxNDigit).
  90                     filter(N -> isPrime(N)).
  91                     forEach(System.out::println);
  92         } catch (NumberFormatException nfe) {
  93             usage();
  94         }
  95     }
  96 
  97     /**
  98      * Decide if a BigInteger is a prime number
  99      *
 100      * @param integer a number
 101      * @return true if integer is a prime number false if integer is not a prime
 102      * number
 103      */
 104     private static boolean isPrime(long number) {
 105         //This is a parall version that checks if a number is a prime number
 106         return !LongStream.range(2L, Math.round(Math.sqrt(number))).parallel().
 107                 anyMatch(divisor -> number % divisor == 0);
 108     }
 109 
 110     /**
 111      * Usage of this program
 112      */
 113     public static void usage() {
 114         System.out.println("Usage: java RandomPrimeNumber lentgh［size]");
 115         System.out.println("length is a positive integer not greater than 16");
 116         System.out.println("size is a positive integer");
 117     }
 118 }