进入buffer.java这个java文件
* <p> There is one subclass of this class for each non-boolean primitive type.
对于不同的数据类型都有相应的子类,除了boolean类型
* <h2> Transferring data </h2>
* 传输数据
* <p> Each subclass of this class defines two categories of <i>get</i> and
* <i>put</i> operations: </p>
* 每一个子类都定义了两种操作 get和out
* <blockquote>
*
* <p> <i>Relative</i> operations read or write one or more elements starting
* at the current position and then increment the position by the number of
* elements transferred.
相对操作 从当前位置 读或者写一个或者多个元素 position你增加相应的数量
If the requested transfer exceeds the limit then a
* relative <i>get</i> operation throws a {@link BufferUnderflowException}
* and a relative <i>put</i> operation throws a {@link
* BufferOverflowException}; in either case, no data is transferred. </p>
* 如果get操作超过了limit的限制,会抛出BufferUnderflowException
如果put操作闯过了limit的限制,会抛出BufferOverflowException
* <p> <i>Absolute</i> operations take an explicit element index and do not
* affect the position. Absolute <i>get</i> and <i>put</i> operations throw
* an {@link IndexOutOfBoundsException} if the index argument exceeds the
* limit. </p>
* 绝对的操作(直接操作索引,不会影响position),绝对的get和put如果超过了 IndexOutOfBoundsException
* </blockquote>
*
* <p> Data may also, of course, be transferred in to or out of a buffer by the
* I/O operations of an appropriate channel, which are always relative to the
* current position.
<h2> Marking and resetting </h2>
*
* <p> A buffer's <i>mark</i> is the index to which its position will be reset
* when the {@link #reset reset} method is invoked.
当调用这个方法的时候,会回到mark标记的位置
The mark is not always
* defined, but when it is defined it is never negative and is never greater
* than the position.
mark不经常使用,但是在使用的时候不可能为负数,并且不可能比position的值要大
If the mark is defined then it is discarded when the
* position or the limit is adjusted to a value smaller than the mark.
mark会被废弃,当position和limit被修改成比mark还要小的值
If the
* mark is not defined then invoking the {@link #reset reset} method causes an
* {@link InvalidMarkException} to be thrown.
mark和reset要成对的定义,否则会抛出异常
<h2> Invariants </h2>
*
* <p> The following invariant holds for the mark, position, limit, and
* capacity values:
*
* <blockquote>
* <tt>0</tt> <tt><=</tt>
* <i>mark</i> <tt><=</tt>
* <i>position</i> <tt><=</tt>
* <i>limit</i> <tt><=</tt>
* <i>capacity</i>
* </blockquote>
* 大小关系 0 <= mark <= position <= limit <=capacity
* <p> A newly-created buffer always has a position of zero and a mark that is
* undefined.
新创建的buffer是0而且mark未被定义
The initial limit may be zero, or it may be some other value
* that depends upon the type of the buffer and the manner in which it is
* constructed.
limit初始化时有可能为0,也有可能是其他值,取决于他的结构
Each element of a newly-allocated buffer is initialized
* to zero.
新定义的buffer的元素位置都为空
