java.lang.io包的使用

 1 String source = "ABCDEF123456";
 2         int mid = source.length() / 2;
 3
 4         ByteArrayInputStream bytesIS = new ByteArrayInputStream(source.getBytes());
 5
 6         // 1. 顺序读取流
 7         int b = 0;
 8         while( -1 != (b = bytesIS.read())){
 9             System.out.print(Integer.toHexString(b) + " ");
10         }
11         System.out.println();
12
13         // 2. 读取完毕之后 调用 read 始终返回 -1
14         b = bytesIS.read();
15         System.out.println(b);
16
17         // 对流进行重置
18         int index = 0;
19         bytesIS.reset();
20         while( -1 != (b = bytesIS.read())){
21             if(index++ == mid && bytesIS.markSupported()){
22                 bytesIS.reset();
23             }
24             System.out.print(Integer.toHexString(b) + " ");
25         }
26         System.out.println();
27
28         // 标记流
29         index = 0;
30         bytesIS.reset();
31         while( -1 != (b = bytesIS.read())){
32             if(index++ == mid && bytesIS.markSupported()){
33 //                bytesIS.reset();
34                 bytesIS.mark(0);
35             }
36             System.out.print(Integer.toHexString(b) + " ");
37         }
38         System.out.println();
39         bytesIS.reset();
40         while( -1 != (b = bytesIS.read())){
41             System.out.print(Integer.toHexString(b) + " ");
42         }
43         System.out.println();
44         bytesIS.reset();
45         while( -1 != (b = bytesIS.read())){
46             System.out.print(Integer.toHexString(b) + " ");
47         }
48         System.out.println();
49
50         // 1. 读取文件 使用 FileInputStream 只能
51         File file = new File("e:/test.txt");
52         System.out.println(file.length());
53         FileInputStream FileIS  = new FileInputStream(file);
54         while( -1 != (b = FileIS.read())){
55             System.out.print("0x" + Integer.toHexString(b) + " ");
56         }
57         System.out.println();
58
59         // 可以使用seek方法来随机的读取文件,但是对于 RandomAccessFile，并不是流类，
60         String mode = "r";
61         RandomAccessFile randomFile = new RandomAccessFile(file, mode);
62         while( -1 != (b = randomFile.read())){
63             System.out.print("0x" + Integer.toHexString(b) + " ");
64         }
65         System.out.println();
66         System.out.println(randomFile.getFilePointer());
67         System.out.println(randomFile.length());
68         randomFile.seek(6);
69         while( -1 != (b = randomFile.read())){
70             System.out.print("0x" + Integer.toHexString(b) + " ");
71         }
72         System.out.println();
73         randomFile.seek(0);
74         while( -1 != (b = randomFile.read())){
75             System.out.print("0x" + Integer.toHexString(b) + " ");
76         }
77         System.out.println();
78
79         // java.lang包中有一个文本描述的工具类 但是其提供的功能也是顺序读取。
80         // java.util.Scanner
81         Scanner scanner = new Scanner(file);
82         System.out.println(scanner.next());
83         scanner = scanner.reset();
84
85         // java.io.PushbackInputStream 过滤流
86         // 这个流提供了 unread 方法, 回退到缓冲区，
87         bytesIS.reset();
88         PushbackInputStream pis = new PushbackInputStream(bytesIS);
89         pis.unread(0x30);
90         System.out.println(Integer.toHexString(pis.read()));
91         System.out.println(Integer.toHexString(pis.read()));
92
93         // 到目前为止，只有流类基本上只能按流的顺序来读写。
94         ByteArrayOutputStream bytesOutPut = new ByteArrayOutputStream();
95         bytesOutPut.write(source.getBytes());
96         System.out.println(bytesOutPut.toString());
97         bytesOutPut.write(0x30);
98         System.out.println(bytesOutPut.toString());
99