The FileInputStream class creates an InputStream that you can use to read bytes from a file. Two commonly used constructors are shown here:

FileInputStream(String filePath)
FileInputStream(File fileObj)

Either can throw a FileNotFoundException. Here, filePath is the full path name of a file, and fileObj is a File object that describes the file.

The following example creates two FileInputStreams that use the same disk file and each of the two constructors:

FileInputStream f0 = new FileInputStream("/autoexec.bat")
File f = new File("/autoexec.bat");
FileInputStream f1 = new FileInputStream(f);

Although the first constructor is probably more commonly used, the second allows you to closely examine the file using the File methods, before attaching it to an input stream. When a FileInputStream is created, it is also opened for reading. FileInputStream overrides six of the methods in the abstract class InputStream. The mark( ) and reset( ) methods are not overridden, and any attempt to use reset( ) on a FileInputStream will generate an IOException.

The next example shows how to read a single byte, an array of bytes, and a subrange of an array of bytes. It also illustrates how to use available( ) to determine the number of bytes remaining and how to use the skip( ) method to skip over unwanted bytes. The program reads its own source file, which must be in the current directory. Notice that it uses the try-with-resources statement to automatically close the file when it is no longer needed.