Java provides many classes for performing text I/O and binary I/O. Files can be classified as either text or binary. A file that can be processed (read, created, or modified) using a text editor such as Notepad on Windows or vi on UNIX is called a text file. All the other files are called binary files. You cannot read binary files using a text editor—they are designed to be read by programs. For example, Java source programs are text files and can be read by a text editor, but Java class files are binary files and are read by the JVM.

Although it is not technically precise and correct, you can envision a text file as consisting of a sequence of characters and a binary file as consisting of a sequence of bits. Characters in a text file are encoded using a character encoding scheme such as ASCII or Unicode. For example, the decimal integer 199 is stored as a sequence of three characters 1, 9, 9 in a text file, and the same integer is stored as a byte-type value C7 in a binary file, because decimal 199 equals hex C7 (199 = 12 * 161 + 7). The advantage of binary files is that they are more efficient to process than text files.

Java offers many classes for performing file input and output. These can be categorized as text I/O classes and binary I/O classes