nio缓冲对象

Posted 2021-01-05 kill-9

 1 package edzy.nio;
 2 
 3 import org.junit.Test;
 4 
 5 import java.nio.ByteBuffer;
 6 
 7 public class ByteNIO {
 8 
 9     @Test
10     public void byteBuf(){
11         ByteBuffer buf = ByteBuffer.allocate(1024);
12         System.out.println("---allocate缓冲---");
13         System.out.println(buf.position());
14         System.out.println(buf.limit());
15         System.out.println(buf.capacity());
16 
17         System.out.println("---put存数据---");
18         String text = "NIO";
19         buf.put(text.getBytes());
20         System.out.println(buf.position());
21         System.out.println(buf.limit());
22         System.out.println(buf.capacity());
23 
24         System.out.println("---flip切换到读模式---");
25         buf.flip();
26         System.out.println(buf.position());
27         System.out.println(buf.limit());
28         System.out.println(buf.capacity());
29 
30 
31         System.out.println("---get读数据---");
32         byte[] dest = new byte[buf.limit()];
33         buf.get(dest);
34         System.out.println(buf.position());
35         System.out.println(buf.limit());
36         System.out.println(buf.capacity());
37         System.out.println(new String(dest));
38 
39 
40         System.out.println("---rewind重新读数据---");
41         buf.rewind();
42         System.out.println(buf.position());
43         System.out.println(buf.limit());
44         System.out.println(buf.capacity());
45 
46         System.out.println("---clear清除指针---");
47         buf.clear();
48         System.out.println(buf.position());
49         System.out.println(buf.limit());
50         System.out.println(buf.capacity());
51 
52 
53     }
54 
55     @Test
56     public void mark(){
57 
58         ByteBuffer buf = ByteBuffer.allocate(100);
59         String str = "mvn compile";
60         buf.put(str.getBytes());
61         buf.flip();
62         byte[] dest = new byte[buf.limit()];
63         buf.get(dest,0,4);
64         System.out.println(new String(dest,0,4));
65         System.out.println(buf.position());
66 
67         //mark标记
68         buf.mark();
69         buf.get(dest,4,4);
70         System.out.println(new String(dest,0,8));
71         System.out.println(buf.position());
72 
73         //指针设置为mark标记所在的位置
74         buf.reset();
75         System.out.println(buf.position());
76 
77         //是否有下一个元素
78         if(buf.hasRemaining()){
79             //缓冲区中的剩余元素数
80             System.out.println(buf.remaining());
81         }
82     }
83     @Test
84     public void direct(){
85         ByteBuffer buf = ByteBuffer.allocate(100);
86         //直接字节缓冲区
87         ByteBuffer bufd = ByteBuffer.allocateDirect(100);
88         System.out.println(buf.isDirect());
89         System.out.println(bufd.isDirect());
90     }
91 }