Java IO.pdf - Nguyen Dang Binh

Java I/O
If you absolutely must use a console in your applet, the following list shows several thirdparty
consoles that work in Internet Explorer. Some provide additional features over the barebones
implementation of Netscape. Of course, URLs can get stale rather quickly. If for some
reason none of these work for you, you can always do what I did to collect them in the first
place: go to http://developer.java.sun.com/developer and search for "console."
Arial Bardin's Java Console http://www.cadviewer.com/JavaConsole.html
Jamie Cansdale's Java Console and Class
http://www.obsolete.com/people/cansdale/java/java_console/index.htm
Flusher
Frederic Lavigne's Package fr.l2f http://www.l2fprod.com/
1.6.2 System.out
System.out is the first instance of the OutputStream class most programmers encounter. In
fact, it's often encountered before programmers know what a class or an output stream is.
Specifically, System.out is the static out field of the java.lang.System class. It's an
instance of java.io.PrintStream, a subclass of java.io.OutputStream.
System.out corresponds to stdout in Unix or C. Normally, output sent to System.out
appears on the console. As a general rule, the console converts the numeric byte data
System.out sends to it into ASCII or ISO Latin-1 text. Thus, the following lines write the
string "Hello World!" on the console:
byte[] hello = {72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100, 33, 10,
13};
System.out.write(hello);
1.6.3 System.err
Unix and C programmers are familiar with stderr, which is commonly used for error
messages. stderr is a separate file pointer from stdout, but often means the same thing.
Generally, stderr and stdout both send data to the console, whatever that is. However,
stdout and stderr can be redirected to different places. For instance, output can be
redirected to a file while error messages still appear on the console.
System.err is Java's version of stderr. Like System.out, System.err is an instance of
java.io.PrintStream , a subclass of java.io.OutputStream . System.err is most
commonly used inside the catch clause of a try/catch block like this:
try {
// Do something that may throw an exception.
}
catch (Exception e) {
System.err.println(e);
}
Finished programs shouldn't have much need for System.err, but it is useful while you're
debugging.
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