Sams Teach Yourself Java™ in 24 Hours (Covering Java 7 and Android)

ptg7068951

292 HOUR 20: Reading and Writing Files

20:

21: output = output + newline;

22: byte[] data = output.getBytes();

23: stream.write(data, 0, data.length);

24: }

25:

26: public static void main(String[] arguments) {

27: ConfigWriter cw = new ConfigWriter();

28: }

29: }

When this application is run, it creates a file called program.properties

that contains the following three lines of text:

Output▼

username=max

score=12550

level=5

Reading and Writing Configuration

Properties

Java programs are more versatilewhen they can be configured using com-

mand-line arguments, as you have demonstrated in several applications

created in preceding hours. The java.utilpackage includes a class,

Properties, that enables configuration settings to be loaded from another

source: a text file.

The file can be read like other file sources in Java:

. Create a Fileobject that represents the file.
. Create a FileInputStreamobject from that File object.
. Call load()to retrieve the properties from that input stream.

A properties file has a set of property names followed by an equal sign (=)

and their values. Here’s an example:

username=lepton

lastCommand=open database

windowSize= 32

LISTING 20.3 Continued