Java NIO——2 缓冲区
一、缓冲区基础1、缓冲区并不是多线程安全的。2、属性（容量、上界、位置、标记）capacitylimit 第一个不能被读或写的元素position 下一个要被读或写的元素索引mark 一个备忘位置3、方法操作(1)翻转buffer.flip() 等同于 buffer.limit(buffer.position()).position(0)(2)、释放buffer.flip();for(int i=0; buffer.hasRemaining(); i++)｛ myByteArray[i] = buffer.get();
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public class Unsigned  {      public static short getUnsignedByte (ByteBuffer bb)      {          return ((short)(bb.get(  ) & 0xff));      }        public static void putUnsignedByte (ByteBuffer bb, int value)      {          bb.put ((byte)(value & 0xff));      }        public static short getUnsignedByte (ByteBuffer bb, int position)      {          return ((short)(bb.get (position) & (short)0xff));      }        public static void putUnsignedByte (ByteBuffer bb, int position,          int value)      {          bb.put (position, (byte)(value & 0xff));      }        // ---------------------------        public static int getUnsignedShort (ByteBuffer bb)      {          return (bb.getShort(  ) & 0xffff);      }        public static void putUnsignedShort (ByteBuffer bb, int value)      {          bb.putShort ((short)(value & 0xffff));      }       public static int getUnsignedShort (ByteBuffer bb, int position)      {          return (bb.getShort (position) & 0xffff);      }        public static void putUnsignedShort (ByteBuffer bb, int position,          int value)      {          bb.putShort (position, (short)(value & 0xffff));      }        // ---------------------------        public static long getUnsignedInt (ByteBuffer bb)        {          return ((long)bb.getInt(  ) & 0xffffffffL);      }        public static void putUnsignedInt (ByteBuffer bb, long value)      {          bb.putInt ((int)(value & 0xffffffffL));      }        public static long getUnsignedInt (ByteBuffer bb, int position)      {          return ((long)bb.getInt (position) & 0xffffffffL);      }        public static void putUnsignedInt (ByteBuffer bb, int position,          long value)      {          bb.putInt (position, (int)(value & 0xffffffffL));      }  }


6、内存映射缓冲区映射缓冲区是带有存储在文件，通过内存映射来存取数据元素的字节缓冲区。映射缓冲区通常是直接存取内存的，只能通过 FileChannel 类创建。