java.lang.io包的使用

String source = "ABCDEF123456";
        int mid = source.length() / 2;
        
        ByteArrayInputStream bytesIS = new ByteArrayInputStream(source.getBytes());
        
        // 1. 顺序读取流
        int b = 0;
        while( -1 != (b = bytesIS.read())){
            System.out.print(Integer.toHexString(b) + " ");
        }
        System.out.println();
        
        // 2. 读取完毕之后 调用 read 始终返回 -1
        b = bytesIS.read();
        System.out.println(b);
        
        // 对流进行重置
        int index = 0;
        bytesIS.reset();
        while( -1 != (b = bytesIS.read())){
            if(index++ == mid && bytesIS.markSupported()){
                bytesIS.reset();
            }
            System.out.print(Integer.toHexString(b) + " ");
        }
        System.out.println();
        
        // 标记流
        index = 0;
        bytesIS.reset();
        while( -1 != (b = bytesIS.read())){
            if(index++ == mid && bytesIS.markSupported()){
//                bytesIS.reset();
                bytesIS.mark(0);
            }
            System.out.print(Integer.toHexString(b) + " ");
        }
        System.out.println();
        bytesIS.reset();
        while( -1 != (b = bytesIS.read())){
            System.out.print(Integer.toHexString(b) + " ");
        }
        System.out.println();
        bytesIS.reset();
        while( -1 != (b = bytesIS.read())){
            System.out.print(Integer.toHexString(b) + " ");
        }
        System.out.println();
        
        // 1. 读取文件 使用 FileInputStream 只能
        File file = new File("e:/test.txt");
        System.out.println(file.length());
        FileInputStream FileIS  = new FileInputStream(file);
        while( -1 != (b = FileIS.read())){
            System.out.print("0x" + Integer.toHexString(b) + " ");
        }
        System.out.println();

        // 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，
        String mode = "r";
        RandomAccessFile randomFile = new RandomAccessFile(file, mode);
        while( -1 != (b = randomFile.read())){
            System.out.print("0x" + Integer.toHexString(b) + " ");
        }
        System.out.println();
        System.out.println(randomFile.getFilePointer());
        System.out.println(randomFile.length());
        randomFile.seek(6);
        while( -1 != (b = randomFile.read())){
            System.out.print("0x" + Integer.toHexString(b) + " ");
        }
        System.out.println();
        randomFile.seek(0);
        while( -1 != (b = randomFile.read())){
            System.out.print("0x" + Integer.toHexString(b) + " ");
        }
        System.out.println();
        
        // 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。
        // java.util.Scanner
        Scanner scanner = new Scanner(file);
        System.out.println(scanner.next());
        scanner = scanner.reset();
        
        // java.io.PushbackInputStream 过滤流
        // 这个流提供了 unread 方法, 回退到缓冲区，
        bytesIS.reset();
        PushbackInputStream pis = new PushbackInputStream(bytesIS);
        pis.unread(0x30);
        System.out.println(Integer.toHexString(pis.read()));
        System.out.println(Integer.toHexString(pis.read()));

        // 到目前为止，只有流类基本上只能按流的顺序来读写。
        ByteArrayOutputStream bytesOutPut = new ByteArrayOutputStream();
        bytesOutPut.write(source.getBytes());
        System.out.println(bytesOutPut.toString());
        bytesOutPut.write(0x30);
        System.out.println(bytesOutPut.toString());