Lesson: Basic I/O

This lesson covers the Java platform classes used for basic I/O. It first focuses on I/O Streams , a powerful concept that greatly simplifies I/O operations. The lesson also looks at serialization, which lets a program write whole objects out to streams and read them back again. Then the lesson looks at file I/O and file system operations, including random access files.

Most of the classes covered in the I/O Streams section are in the java.io package. Most of the classes covered in the File I/O section are in the java.nio.file package.

I/O Streams

File I/O (Featuring NIO.2)


A summary of the key points covered in this trail.

Questions and Exercises

Test what you've learned in this trail by trying these questions and exercises.

The I/O Classes in Action

Many of the examples in the next trail, Custom Networking use the I/O streams described in this lesson to read from and write to network connections.

Security consideration:

Some I/O operations are subject to approval by the current security manager. The example programs contained in these lessons are standalone applications, which by default have no security manager. To work in an applet, most of these examples would have to be modified. See What Applets Can and Cannot Do for information about the security restrictions placed on applets.