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();         }      }}