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.concurrent.ThreadLocalRandom;
43 import java.util.stream.IntStream;
44
45 /**
46 * This demo shows how to use the parallel mode to find several number for given
47 * length prime number. The process easily use a parallel stream to generate
48 * a number of desired length probable prime number. Following with filter
49 * operation to make sure we will get desirable length prime numbers.
50 *
51 * @author tyan
52 */
53 public class ProbablePrimeNumber {
54 /**
55 * Try to get length from command line. Use the length to create random long
56 * stream, that integer's digit is length.
57 *
58 * @param args This has to be a 1-element or 2-elements array, The first
59 * element must be a positive number, which equals to length of generated
60 * prime number stream. Second element is optional, it will be used as how
61 * many probable prime number that will be generated if it's set.
62 */
63 private static int DEFAULT_NUM = 1 << 10;
64
65 public static void main(String[] args) {
66 if (args.length != 1 && args.length != 2) {
67 usage();
68 return;
69 }
70 try {
71 int expectedLength = Integer.parseInt(args[0]);
72 int size = (args.length == 2) ?
73 Integer.parseInt(args[1]) :
74 DEFAULT_NUM;
75 IntStream.range(0, size).
76 parallel().
77 mapToObj(i ->
78 BigInteger.probablePrime(expectedLength * 10 / 3 -
79 ThreadLocalRandom.current().nextInt(3),
80 ThreadLocalRandom.current())).
81 filter(c -> c.toString().length() == expectedLength).
82 forEach(prime ->
83 System.out.println("Found a probable prime number :"
84 + prime));
85 } catch (NumberFormatException nfe) {
86 usage();
87 }
88 }
89
90 /**
91 * Usage of this program
92 */
93 public static void usage() {
94 System.out.println("Usage: java ProbablePrimeNumber lentgh [size]");
95 System.out.println("size is a positive integer");
96 }
97 }