Java基础之写文件——将多个字符串写入到文件中（WriteProverbs）

控制台程序，将一系列有用的格言写入到文件中。

本例使用通道把不同长度的字符串写入到文件中，为了方便从文件中恢复字符串，将每个字符串的长度写入到文件中紧靠字符串本身前面的位置，这可以告知在读取字符串之前字符串中存在的字符数目，也可以使用视图缓冲区来读取字符串。

 import static java.nio.file.StandardOpenOption.*;
 import java.nio.file.*;
 import java.nio.channels.*;

 import java.util.EnumSet;
 import java.io.IOException;
 import java.nio.ByteBuffer;

 public class WriteProverbs {
   public static void main(String[] args) {
     String[] sayings = {
       "Indecision maximizes flexibility.",
       "Only the mediocre are always at their best.",
       "A little knowledge is a dangerous thing.",
       "Many a mickle makes a muckle.",
       "Who begins too much achieves little.",
       "Who knows most says least.",
       "A wise man sits on the hole in his carpet."
     };

     Path file = Paths.get(System.getProperty("user.home")).resolve("Beginning Java Struff").resolve("Proverbs.txt");// Path object for the file
     try {
       Files.createDirectories(file.getParent());                       // Make sure we have the directory
     } catch (IOException e) {
       e.printStackTrace();
       System.exit(1);
     }

     // The buffer must accommodate the longest string
     // so we find the length of the longest string
     int maxLength = 0;
     for (String saying : sayings) {
       if(maxLength < saying.length())
         maxLength = saying.length();
     }
     // The buffer length must hold the longest string
     // plus its length as a binary integer
     // Each character needs 2 bytes and an integer 4 bytes
     ByteBuffer buf = ByteBuffer.allocate(2*maxLength + 4);

     try (WritableByteChannel channel = Files.newByteChannel(file, EnumSet.of(WRITE, CREATE, APPEND))) {

      for (String saying : sayings) {
         buf.putInt(saying.length()).asCharBuffer().put(saying);
         buf.position(buf.position() + 2*saying.length()).flip();
         channel.write(buf);                                            // Write the buffer to the file channel
         buf.clear();
       }
       System.out.println("Proverbs written to file.");
     } catch (IOException e) {
       e.printStackTrace();
     }
   }
 }