• 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         
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  • 原文地址:https://www.cnblogs.com/a-ray-of-sunshine/p/4564287.html
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