Java The Complete Reference, Seventh Edition

To write to the console by using aPrintWriter, specifySystem.outfor the output stream

and flush the stream after each newline. For example, this line of code creates aPrintWriter

that is connected to console output:

PrintWriter pw = new PrintWriter(System.out, true);

The following application illustrates using aPrintWriterto handle console output:

// Demonstrate PrintWriter

import java.io.*;

public class PrintWriterDemo {

public static void main(String args[]) {

PrintWriter pw = new PrintWriter(System.out, true);

pw.println("This is a string");

int i = -7;

pw.println(i);

double d = 4.5e-7;

pw.println(d);

}

}

The output from this program is shown here:

This is a string

-7

4.5E-7

Remember, there is nothing wrong with usingSystem.outto write simple text output

to the console when you are learning Java or debugging your programs. However, using a

PrintWriterwill make your real-world applications easier to internationalize. Because no

advantage is gained by using aPrintWriterin the sample programs shown in this book, we

will continue to useSystem.outto write to the console.

Reading and Writing Files

Java provides a number of classes and methods that allow you to read and write files. In Java,

all files are byte-oriented, and Java provides methods to read and write bytes from and to a

file. However, Java allows you to wrap a byte-oriented file stream within a character-based

object. This technique is described in Part II. This chapter examines the basics of file I/O.

Two of the most often-used stream classes areFileInputStreamandFileOutputStream,

which create byte streams linked to files. To open a file, you simply create an object of one of

these classes, specifying the name of the file as an argument to the constructor. While both

classes support additional, overridden constructors, the following are the forms that we will

be using:

FileInputStream(StringfileName) throws FileNotFoundException

FileOutputStream(StringfileName) throws FileNotFoundException

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