程序员做网站如何赚钱,wordpress 显示pdf插件下载,做我的狗在什么网站上看,服装网站网络建设和硬件资源控制台程序#xff0c;上一条博文#xff08;PrimesToFile2#xff09;每次将一个素数写入到文件中#xff0c;所以效率不是很高。最好是使用更大的缓冲区并加载多个素数。 本例重复使用三个不同的视图缓冲区加载字节缓冲区并尽可能加入更多的素数#xff0c;推荐使用这种…控制台程序上一条博文PrimesToFile2每次将一个素数写入到文件中所以效率不是很高。最好是使用更大的缓冲区并加载多个素数。 本例重复使用三个不同的视图缓冲区加载字节缓冲区并尽可能加入更多的素数推荐使用这种方式。 1 import static java.lang.Math.ceil;2 import static java.lang.Math.sqrt;3 import static java.lang.Math.min;4 import static java.nio.file.StandardOpenOption.*;5 import java.nio.file.*;6 import java.nio.channels.*;7 import java.nio.*;8 import java.util.*;9 import java.io.IOException;
10
11 public class PrimesToFile3 {
12 public static void main(String[] args) {
13 int primesRequired 100; // Default count
14 if (args.length 0) {
15 try {
16 primesRequired Integer.valueOf(args[0]).intValue();
17 } catch (NumberFormatException e) {
18 System.out.println(Prime count value invalid. Using default of primesRequired);
19 }
20 }
21
22 long[] primes new long[primesRequired]; // Array to store primes
23
24 getPrimes(primes);
25 Path file createFilePath(Beginning Java Struff,primesAgain.txt);
26 writePrimesFile(primes,file);
27 }
28 //Calculate enough primes to fill the array
29 private static long[] getPrimes(long[] primes) {
30 primes[0] 2L; // Seed the first prime
31 primes[1] 3L; // and the second
32 // Count of primes found ?up to now, which is also the array index
33 int count 2;
34 // Next integer to be tested
35 long number 5L;
36
37 outer:
38 for (; count primes.length; number 2) {
39
40 // The maximum divisor we need to try is square root of number
41 long limit (long)ceil(sqrt((double)number));
42
43 // Divide by all the primes we have up to limit
44 for (int i 1 ; i count primes[i] limit ; i)
45 if (number % primes[i] 0L) // Is it an exact divisor?
46 continue outer; // yes, try the next number
47
48 primes[count] number; // We got one!
49 }
50 return primes;
51 }
52 //Create the path for the named file in the specified directory
53 //in the user home directory
54 private static Path createFilePath(String directory, String fileName) {
55 Path file Paths.get(System.getProperty(user.home)).resolve(directory).resolve(fileName);
56 try {
57 Files.createDirectories(file.getParent()); // Make sure we have the directory
58 } catch (IOException e) {
59 e.printStackTrace();
60 System.exit(1);
61 }
62 System.out.println(New file is: file);
63 return file;
64 }
65
66 //Write the array contents to file
67 private static void writePrimesFile(long[] primes, Path file) {
68 final int BUFFERSIZE 1024; // Byte buffer size
69 try (WritableByteChannel channel Files.newByteChannel( file, EnumSet.of(WRITE, CREATE))){
70 ByteBuffer buf ByteBuffer.allocate(BUFFERSIZE);
71 String primeStr null;
72 int primesWritten 0;
73 while (primesWritten primes.length) {
74 while (primesWritten primes.length) {
75 primeStr prime primes[primesWritten];
76 if ((buf.position() 2*primeStr.length() 16) buf.limit()) {
77 break;
78 }
79 buf.asDoubleBuffer().put(0, (double)primeStr.length());
80 buf.position(buf.position() 8);
81 buf.position(buf.position() 2*buf.asCharBuffer().put(primeStr).position());
82 buf.asLongBuffer().put(primes[primesWritten]);
83 buf.position(buf.position() 8);
84 }
85 buf.flip();
86 channel.write(buf);
87 buf.clear();
88 }
89 System.out.println(File written is ((FileChannel)channel).size() bytes.);
90 } catch (IOException e) {
91 e.printStackTrace();
92 }
93 }
94 } 转载于:https://www.cnblogs.com/mannixiang/p/3386796.html
