BIO与NIO的方式实现文件拷贝

面试题 - 编程实现文件拷贝。（这个题目在笔试的时候经常出现，下面的代码给出了两种实现方案）

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

public final class Main {

    private Main() {
        throw new AssertionError();
    }

  /**
     * IO文件拷贝
     * @param source 被拷贝的源文件
     * @param target 拷贝出来的目的文件
     * @throws IOException
     */
    public static void fileCopy(String source, String target) throws IOException {
          InputStream in = new FileInputStream(source);
          OutputStream out = new FileOutputStream(target);
          byte[] buffer = new byte[4096];
          int bytesToRead;
          while((bytesToRead = in.read(buffer)) != -1) {
              out.write(buffer, 0, bytesToRead);
          }
      }
/**
     * nio实现文件拷贝
     * @param source
     * @param target
     * @throws IOException
     */
     public static void fileCopyNIO(String source, String target) throws IOException {
         FileInputStream in = new FileInputStream(source);
         FileOutputStream out = new FileOutputStream(target);
         FileChannel inChannel = in.getChannel();
         FileChannel outChannel = out.getChannel();
         ByteBuffer buffer = ByteBuffer.allocate(4096);
         while(inChannel.read(buffer) != -1) {
             buffer.flip();
             outChannel.write(buffer);
             buffer.clear();
         }
      }

}