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

• Byte Streams handle I/O of raw binary data.
• Character Streams handle I/O of character data, automatically handling translation to and from the local character set.
• Buffered Streams optimize input and output by reducing the number of calls to the native API.
• Scanning and Formatting allows a program to read and write formatted text.
• I/O from the Command Line describes the Standard Streams and the Console object.
• Data Streams handle binary I/O of primitive data type and String values.
• Object Streams handle binary I/O of objects.

File I/O (Featuring NIO.2)

• What is a Path? examines the concept of a path on a file system.
• The Path Class introduces the cornerstone class of the java.nio.file package.
• Path Operations looks at methods in the Path class that deal with syntactic operations.
• File Operations introduces concepts common to many of the file I/O methods.
• Checking a File or Directory shows how to check a file's existence and its level of accessibility.
• Deleting a File or Directory.
• Copying a File or Directory.
• Moving a File or Directory.
• Managing Metadata explains how to read and set file attributes.
• Reading, Writing and Creating Files shows the stream and channel methods for reading and writing files.
• Random Access Files shows how to read or write files in a non-sequentially manner.
• Creating and Reading Directories covers API specific to directories, such as how to list a directory's contents.
• Links, Symbolic or Otherwise covers issues specific to symbolic and hard links.
• Walking the File Tree demonstrates how to recursively visit each file and directory in a file tree.
• Finding Files shows how to search for files using pattern matching.
• Watching a Directory for Changes shows how to use the watch service to detect files that are added, removed or updated in one or more directories.
• Other Useful Methods covers important API that didn't fit elsewhere in the lesson.
• Legacy File I/O Code shows how to leverage Path functionality if you have older code using the java.io.File class. A table mapping java.io.File API to java.nio.file API is provided.

Summary

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.