Java IO.pdf - Nguyen Dang Binh

public void writeInt(int i) throws IOException {
}
out.write(i & 0xFF);
out.write((i >>> 8) & 0xFF);
out.write((i >>> 16) & 0xFF);
// What happens if another thread preempts here?
out.write((i >>> 24) & 0xFF);
written += 4;
Java I/O
Suppose a second thread preempts the running thread where indicated in the previous code
and writes unrelated data onto the output stream. The entire stream can be corrupted, because
the bytes of the int are separated. The same synchronization tricks work here as well.
However, all the problems I've noted here are shared by DataInputStream and
DataOutputStream. Similar problems crop up in other filter stream classes. This leads to the
following general principle for thread-safe programming:
Never allow two threads to share a stream.
The principle is most obvious for filter streams, but it applies to regular streams as well.
Although writing or reading a single byte can be treated as an atomic operation, many
programs will not be happy to read and write individual bytes. They'll want to read or write a
particular group of bytes and will not react well to being interrupted.
7.10 File Viewer, Part 3
In Chapter 4, I introduced a FileDumper program that could print the raw bytes of a file in
ASCII, hexadecimal, or decimal. In this chapter, I'm going to expand that program so that it
can interpret the file as containing binary numbers of varying widths. In particular I'm going
to make it possible to dump a file as shorts, unsigned shorts, ints, longs, floats, and
doubles. Integer types may be either big-endian or little-endian. The main class,
FileDumper3, is shown in Example 7.10. As in Chapter 4, this program reads a series of
filenames and arguments from the command line in the main() method. Each filename is
passed to a method that opens a file input stream from the file. Depending on the commandline
arguments, a particular subclass of DumpFilter from Chapter 6 is selected and chained to
the input stream. Finally, the StreamCopier.copy() method pours data from the input stream
onto System.out.
Example 7.10. The FileDumper3 Class
import java.io.*;
import com.macfaq.io.*;
public class FileDumper3 {
public static final int ASC = 0;
public static final int DEC = 1;
public static final int HEX = 2;
public static final int SHORT = 3;
public static final int INT = 4;
public static final int LONG = 5;
public static final int FLOAT = 6;
public static final int DOUBLE = 7;
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