The commons-io component contains utility classes, filters, streams, readers and writers.

See: Description

Packages 
Package Description
org.apache.commons.io
This package defines utility classes for working with streams, readers, writers and files.
org.apache.commons.io.filefilter
This package defines an interface (IOFileFilter) that combines both FileFilter and FilenameFilter.
org.apache.commons.io.input
This package provides implementations of input classes, such as InputStream and Reader.
org.apache.commons.io.output
This package provides implementations of output classes, such as OutputStream and Writer.

The commons-io component contains utility classes, filters, streams, readers and writers.

These classes aim to add to the standard JDK IO classes. The utilities provide convenience wrappers around the JDK, simplifying various operations into pre-tested units of code. The filters and streams provide useful implementations that perhaps should be in the JDK itself.