java.nio.ByteBuffer中flip、rewind、clear方法的区别
2017-07-03 13:05
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对缓冲区的读写操作首先要知道缓冲区的下限、上限和当前位置。下面这些变量的值对Buffer类中的某些操作有着至关重要的作用:
limit:所有对Buffer读写操作都会以limit变量的值作为上限。
position:代表对缓冲区进行读写时,当前游标的位置。
capacity:代表缓冲区的最大容量(一般新建一个缓冲区的时候,limit的值和capacity的值默认是相等的)。
flip、rewind、clear这三个方法便是用来设置这些值的。
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/d3e11f2c1822f59bc56f79f24a08f007.gif)
public final Buffer clear()
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/b3c65e8687730e8a4a367258f82ba420.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
position = 0; //重置当前读写位置
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
limit = capacity;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
mark = -1; //取消标记
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
return this;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/710abe1fe442cbbae1b47eb83780c3c5.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/d3e11f2c1822f59bc56f79f24a08f007.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/d3e11f2c1822f59bc56f79f24a08f007.gif)
clear方法将缓冲区清空,一般是在重新写缓冲区时调用。
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/b3c65e8687730e8a4a367258f82ba420.gif)
public final Buffer flip() {
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
limit = position;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
position = 0;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
mark = -1;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
return this;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/710abe1fe442cbbae1b47eb83780c3c5.gif)
}
反转缓冲区。首先将限制设置为当前位置,然后将位置设置为 0。如果已定义了标记,则丢弃该标记。 常与compact方法一起使用。通常情况下,在准备从缓冲区中读取数据时调用flip方法。
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/b3c65e8687730e8a4a367258f82ba420.gif)
public final Buffer rewind() {
2
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
position = 0;
3
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
mark = -1;
4
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
return this;
5
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/710abe1fe442cbbae1b47eb83780c3c5.gif)
}
以上三种方法均使用final修饰,java.nio.Buffer的所有子类均使用同一种flip、clear和rewind机制。
limit:所有对Buffer读写操作都会以limit变量的值作为上限。
position:代表对缓冲区进行读写时,当前游标的位置。
capacity:代表缓冲区的最大容量(一般新建一个缓冲区的时候,limit的值和capacity的值默认是相等的)。
flip、rewind、clear这三个方法便是用来设置这些值的。
clear方法
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/d3e11f2c1822f59bc56f79f24a08f007.gif)
public final Buffer clear()
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/b3c65e8687730e8a4a367258f82ba420.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
position = 0; //重置当前读写位置
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
limit = capacity;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
mark = -1; //取消标记
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
return this;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/710abe1fe442cbbae1b47eb83780c3c5.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/d3e11f2c1822f59bc56f79f24a08f007.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/d3e11f2c1822f59bc56f79f24a08f007.gif)
clear方法将缓冲区清空,一般是在重新写缓冲区时调用。
flip方法
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/b3c65e8687730e8a4a367258f82ba420.gif)
public final Buffer flip() {
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
limit = position;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
position = 0;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
mark = -1;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
return this;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/710abe1fe442cbbae1b47eb83780c3c5.gif)
}
反转缓冲区。首先将限制设置为当前位置,然后将位置设置为 0。如果已定义了标记,则丢弃该标记。 常与compact方法一起使用。通常情况下,在准备从缓冲区中读取数据时调用flip方法。
rewind方法
1![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/b3c65e8687730e8a4a367258f82ba420.gif)
public final Buffer rewind() {
2
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
position = 0;
3
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
mark = -1;
4
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/6b9e4acc8ea6eee405e50d7f091221a2.gif)
return this;
5
![](https://oscdn.geek-share.com/Uploads/Images/Content/201911/04/710abe1fe442cbbae1b47eb83780c3c5.gif)
}
以上三种方法均使用final修饰,java.nio.Buffer的所有子类均使用同一种flip、clear和rewind机制。
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