Java I/O

Chapter 4. File Streams

Until now, most of the examples in this book have used the streams System.in and System.out. These are convenient for examples, but in real life, you’ll more commonly attach streams to data sources like files and network connections. You’ll use the java.io.FileInputStream and java.io.FileOutputStream classes, which are concrete subclasses of java.io.InputStream and java.io.OutputStream, to read and write files. FileInputStream and FileOutputStream provide input and output streams that let you read and write files. We’ll discuss these classes in detail in this chapter; they provide the standard methods for reading and writing data. What they don’t provide is a mechanism for file-specific operations, like finding out whether a file is readable or writable. For that, you may want to look forward to Chapter 12, which talks about the File class itself and the way Java works with files.

Reading Files

java.io.FileInputStream is a concrete subclass of java.io.InputStream. It provides an input stream connected to a particular file.

public class FileInputStream extends InputStream

FileInputStream has all the usual methods of input streams, such as read(), available(), skip(), and close(), which are used exactly as they are for any other input stream.

public native int read() throws IOException public int read(byte[] data) throws IOException public int read(byte[] data, int offset, int length) throws IOException public native long skip(long n) throws IOException public ...