并不是所有的IO流类都支持NIO操作的，支持的类有FileInputStream、FileOutputStream和RandomAccessFile。

/*文件读取，返回读取内容*/
  public static String fileReader(File fileName){
    
    String fileContent = null;
    FileInputStream fis = null;
    FileChannel fc = null;
    ByteBuffer bb ;
    try {
      fis = new FileInputStream(fileName);
      fc = fis.getChannel();
      // 分配10000字节的非直接缓冲区
      bb = ByteBuffer.allocate(10000);
      /*通过通道将数据读入到bb里面*/
      fc.read(bb);
      /*这里一定不要省略--切换为读取模式*/
      bb.flip();
      fileContent = new String(bb.array());
    } catch (Exception e) {
      e.printStackTrace();
    }finally{
      
      try {
        fc.close();
      } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
      }
      try {
        fis.close();
      } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
      }
    }
    
    return fileContent;
    
  }
  /*
  fileName:要写入的目标文件；
  s:要写入的信息；
   */
  public static void fileWriter(File fileName,String s){
    
    String fileContent = null;
    FileOutputStream fos = null;
    FileChannel fc = null;
    byte[] bts = s.getBytes();
    
    try {
      fc = new FileOutputStream(fileName).getChannel();
      ByteBuffer bb = ByteBuffer.allocate(bts.length);
      /*将bts放入bb里面*/
      bb.put(bts);
      //切换读取模式
      bb.flip();
      /*通过通道从缓冲区块读出到目标文件*/
      fc.write(bb);
    } catch (Exception e) {
      e.printStackTrace();
    }finally{
      try {
        fc.close();
      } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
      }
      try {
        fos.close();
      } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
      }
      
      }
  
  }
  /*进行文件复制*/
  public static void copy(String srcFile,String destFile){
    
    long begin = System.currentTimeMillis();
    FileInputStream fis = null;
    FileOutputStream fos = null;
    FileChannel in = null;
    FileChannel out =null;
    ByteBuffer bb = null;
    
    try {
      /* get NIO read channel */
      fis = new FileInputStream(srcFile);
      in = fis.getChannel();
      /* get NIO write channel*/
      fos = new FileOutputStream(destFile);
      out = fos.getChannel();
      
      bb = ByteBuffer.allocate(100000);
      int len = 0;
      while((len = in.read(bb)) != -1){
        /*在write前，set the limit and position*/
        bb.flip();
        /*write form position to limit */
        out.write(bb);
        /*init positon/limit/capcity,prepare to the next loop*/
        bb.clear();
      }
      long end = System.currentTimeMillis();
      System.out.println("use time ："+(end-begin));
      out.close();
      in.close();
      fos.close();
      fis.close();
    } catch (Exception e) {
      // TODO: handle exception
      e.printStackTrace();
    }
    
  }

参考博文：NIO究竟是什么 ？