Java网络编程【2】缓冲区Buffer的数据读取_读取java缓存数据

1.什么是缓冲区

在Java NIO中负责数据的存取，缓冲区的底层其实就是数组。用于存储不同数据类型的数组。除了八大基本数据类型中的boolean类型，其他的类型都有其对应的缓冲区。

• ByteBuffer
• CharBuffer
• IntBuffer
• ShortBuffer
• LongBuffer
• FloatBuffer
• DoubleBuffer

2.缓存区属性

mark <= position <= limit <= capacity
1

3.缓存区读写操作

String bufferStr = "buffer";

        System.out.println("------------分配缓冲区allocate()-------------");
        ByteBuffer buffer = ByteBuffer.allocate(1024);
        System.out.println(buffer.position());
        System.out.println(buffer.limit());
        System.out.println(buffer.capacity());

        /*  ------------分配缓冲区allocate()-------------
        0
        1024
        1024*/

        System.out.println("------------缓冲区存数据put()-------------");
        buffer.put(bufferStr.getBytes());
        System.out.println(buffer.position());
        System.out.println(buffer.limit());
        System.out.println(buffer.capacity());

        /*------------缓冲区存数据put()-------------
        6
        1024
        1024*/

        System.out.println("------------缓冲区切换到读数据模式flip()-------------");
        buffer.flip();
        System.out.println(buffer.position());
        System.out.println(buffer.limit());
        System.out.println(buffer.capacity());
        
        /*     ------------缓冲区切换到读数据模式flip()-------------
        0
        6
        1024*/

        System.out.println("------------缓冲区读数据get()-------------");
        byte[] bytes = new byte[buffer.limit()];
        buffer.get(bytes);
        System.out.println("缓存区存入的数据是>>>"+new String(bytes));
        System.out.println(buffer.position());
        System.out.println(buffer.limit());
        System.out.println(buffer.capacity());
        
        /*  ------------缓冲区读数据get()-------------
         缓存区存入的数据是>>>buffer
        6
        6
        1024*/

        System.out.println("------------重复读rewind()-------------");
        buffer.rewind();
        System.out.println(buffer.position());
        System.out.println(buffer.limit());
        System.out.println(buffer.capacity());
        
        /*  ------------重复读rewind()-------------
        0
        6
        1024*/
        

        System.out.println("------------清除clear():处于被遗忘状态，起始数据还在-------------");
        buffer.clear();
        System.out.println(buffer.position());
        System.out.println(buffer.limit());
        System.out.println(buffer.capacity());
        
        /*------------清除clear()-------------
        0
        1024
        1024*/
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71

具体实现不做赘述。

4.mark()与reset()

mark()用作position定位，与reset()共同使用，可以使在调用reset()方法时让postion返回到mark()方法调用时的postion。

String str = "buffer";
        ByteBuffer buffer = ByteBuffer.allocate(1024);
        buffer.put(str.getBytes());
        buffer.flip();
        byte[] bytes = new byte[buffer.limit()];
        buffer.get(bytes,0,2);
        System.out.println(new String(bytes,0,2));
        System.out.println(buffer.position());
        System.out.println(buffer.limit());
        System.out.println(buffer.capacity());
        
        /*2
        6
        1024*/
        System.out.println("------------mark()--------------");

        buffer.mark();
        buffer.get(bytes,2,2);
        System.out.println(new String(bytes,2,2));
        System.out.println(buffer.position());
        System.out.println(buffer.limit());
        System.out.println(buffer.capacity());
        /*------------mark()--------------
        ff
        4
        6
        1024*/
        System.out.println("-------------reset()-------------");
        buffer.reset();
        System.out.println(buffer.position());
        System.out.println(buffer.limit());
        System.out.println(buffer.capacity());
        /*-------------reset()-------------
        2
        6
        1024*/
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36