Introduction
Commons IO is a library of utilities to assist with developing IO functionality in Java. It provides various utility classes for common operations for File IO covering a wide range of use cases. It helps avoid writing boilerplate code. It also provides various Comparator implementations for Files.
Some of the main features of Commons IO are:
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IOUtils: A class that contains utility methods for working with streams, readers, writers, and files.
FileUtils: A class that contains utility methods for working with File objects, such as opening, reading, writing, copying, and moving files.
FilenameUtils: A class that contains utility methods for working with filenames without using File objects. It provides an operating-system-agnostic way of executing common functions on file names.
FileSystemUtils: A class that contains utility methods for working with the file system, such as getting the free space on a drive.
TeeInputStream and TeeOutputStream: Classes that allow writing a single input stream to two different output streams, or reading from two different input streams into a single output stream.
File filters and file comparators: Interfaces and classes that provide various criteria for filtering and sorting files.
In this article, we will see how to download and install Commons IO 2.4, and how to use some of its most useful features. We will also compare it with some alternatives and explain the benefits of using Commons IO.
Download and Installation
To use Commons IO 2.4, we need to download the jar file from the official website or from a mirror site. We can also use Maven or Gradle to manage the dependency.
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After downloading the jar file, we need to add it to the classpath of our project. This can be done by adding the jar file to the lib folder of our project, or by configuring the build tool or IDE to include it.
For example, if we are using Maven, we can add the following dependency to our pom.xml file:
<dependency> <groupId>commons-io</groupId> <artifactId>commons-io</artifactId> <version>2.4</version> </dependency>
If we are using Gradle, we can add the following dependency to our build.gradle file:
dependencies implementation 'commons-io:commons-io:2.4'
Utility Classes
Commons IO provides several utility classes that can help us perform common tasks on files. In this section, we will see how to use some of them with examples.
IOUtils
IOUtils contains utility methods for working with streams, readers, writers, and files. These methods can save us a lot of time and code by simplifying common operations such as reading, writing, copying, and closing resources.
For example, suppose we want to read bytes from a URL and print them. We can do this with IOUtils as follows:
InputStream in = new URL(" try System.out.println(IOUtils.toString(in)); finally IOUtils.closeQuietly(in);
This code is much shorter and simpler than using the standard Java classes such as InputStreamReader, BufferedReader, etc. It also handles closing the stream quietly in case of any exception.
FileUtils
FileUtils contains utility methods for working with File objects. These methods can help us perform various operations on files, such as opening, reading, writing, copying, moving, deleting, and comparing files. They can also handle exceptions and close resources automatically.
For example, suppose we want to copy a file from one location to another. We can do this with FileUtils as follows:
File source = new File("C:\\Users\\user\\Documents\\source.txt"); File dest = new File("C:\\Users\\user\\Documents\\dest.txt"); FileUtils.copyFile(source, dest);
This code is much easier and safer than using the standard Java classes such as FileInputStream, FileOutputStream, etc. It also handles any IOException that may occur during the copy operation.
FilenameUtils
FilenameUtils contains utility methods for working with filenames without using File objects. These methods can help us manipulate and extract information from filenames in a platform-independent way. They can also handle various file formats and extensions.
For example, suppose we want to get the base name and extension of a filename. We can do this with FilenameUtils as follows:
String filename = "C:\\Users\\user\\Documents\\report.pdf"; String basename = FilenameUtils.getBaseName(filename); // returns "report" String extension = FilenameUtils.getExtension(filename); // returns "pdf"
This code works regardless of the operating system or the file separator used. It also handles any dot or slash in the filename.
FileSystemUtils
FileSystemUtils contains utility methods for working with the file system. These methods can help us get information about the file system, such as the free space on a drive or partition.
For example, suppose we want to get the free space on the C drive in bytes. We can do this with FileSystemUtils as follows:
long freeSpace = FileSystemUtils.freeSpaceKb("C:"); // returns the free space in kilobytes freeSpace = freeSpace * 1024; // converts to bytes
This code works on Windows, Linux, and Unix systems. It also handles any exception that may occur during the operation.
Input and Output
Commons IO also provides classes that can help us work with input and output streams in a more flexible way. In this section, we will see how to use two of them: TeeInputStream and TeeOutputStream.
TeeInputStream
TeeInputStream is a class that allows writing a single input stream to two different output streams. This can be useful for logging, debugging, or monitoring purposes.
For example, suppose we want to read bytes from a URL and write them to both a file and the console. We can do this with TeeInputStream as follows:
InputStream in = new URL(" OutputStream out1 = new FileOutputStream("C:\\Users\\user\\Documents\\output.txt"); OutputStream out2 = System.out; TeeInputStream tee = new TeeInputStream(in, out1); try IOUtils.copy(tee, out2); finally IOUtils.closeQuietly(tee); IOUtils.closeQuietly(out1);
This code reads bytes from the URL and writes them to both the file and the console simultaneously. It also closes all the streams quietly in case of any exception.
TeeOutputStream
TeeOutputStream is a class that allows reading from two different input streams into a single output stream. This can be useful for merging, combining, or concatenating data from different sources.
For example, suppose we want to read bytes from two files and write them to a single file. We can do this with TeeOutputStream as follows:
InputStream in1 = new FileInputStream("C:\\Users\\user\\Documents\\input1.txt"); InputStream in2 = new FileInputStream("C:\\Users\\user\\Documents\\input2.txt"); OutputStream out = new FileOutputStream("C:\\Users\\user\\Documents\\output.txt"); TeeOutputStream tee = new TeeOutputStream(out, in1); try IOUtils.copy(in2, tee); finally IOUtils.closeQuietly(tee); IOUtils.closeQuietly(in1); IOUtils.closeQuietly(in2);
This code reads bytes from both input files and writes them to the output file sequentially. It also closes all the streams quietly in case of any exception.
Filters
Commons IO also provides interfaces and classes that can help us filter and sort files based on various criteria. In this section, we will see how to use some of them: file filters and file comparators.
File filters
File filters are interfaces and classes that provide various criteria for filtering files. They can be used to select files based on their name, size, date, type, or content. They can also be combined with logical operators such as AND, OR, and NOT.
For example, suppose we want to list all the files in a directory that have the extension .txt and are larger than 1 KB. We can do this with file filters as follows:
File dir = new File("C:\\Users\\user\\Documents"); FileFilter filter = new AndFileFilter( new SuffixFileFilter(".txt"), new SizeFileFilter(1024, false) ); File[] files = dir.listFiles(filter); for (File file : files) System.out.println(file.getName());
This code uses the AndFileFilter to combine two other filters: the SuffixFileFilter that matches files with the given suffix, and the SizeFileFilter that matches files with the given size range. It then lists the files that match both criteria.
File comparators
File comparators are interfaces and classes that provide various criteria for sorting files. They can be used to order files based on their name, size, date, type, or content. They can also be reversed or chained with other comparators.
For example, suppose we want to sort the files in a directory by their name in ascending order and then by their size in descending order. We can do this with file comparators as follows:
File dir = new File("C:\\Users\\user\\Documents"); Comparator comparator = new CompositeFileComparator( new NameFileComparator(), new ReverseComparator(new SizeFileComparator()) ); File[] files = dir.listFiles(); Arrays.sort(files, comparator); for (File file : files) System.out.println(file.getName() + " (" + file.length() + " bytes)");
This code uses the CompositeFileComparator to chain two other comparators: the NameFileComparator that compares files by their name, and the ReverseComparator that reverses the order of another comparator. In this case, it reverses the SizeFileComparator that compares files by their size. It then sorts the files by using both criteria.
Conclusion
In this article, we have seen how to use Commons IO 2.4, a library of utilities for developing IO functionality in Java. We have seen how to download and install the library, and how to use some of its most useful features. We have also compared it with some alternatives and explained the benefits of using Commons IO.
Commons IO can help us simplify and improve our code by providing various utility classes for common operations on files. It can also help us work with input and output streams in a more flexible way. It can also help us filter and sort files based on various criteria.
We recommend using Commons IO whenever we need to deal with IO functionality in Java. It can save us a lot of time and effort, and make our code more readable and reliable.
FAQs
Here are some frequently asked questions about Commons IO:
Q: What are the advantages of using Commons IO over standard Java classes?
A: Some of the advantages are:
Commons IO provides more functionality and features than standard Java classes.
Commons IO handles exceptions and closes resources automatically.
Commons IO is platform-independent and supports various file formats and extensions.
Commons IO is well-tested and widely used by many projects.
Q: What are some alternatives to Commons IO?
A: Some alternatives are:
NIO: A package that provides non-blocking input and output operations for Java. It supports channels, buffers, selectors, and asynchronous operations.
Guava: A library that provides various utilities for Java, including some for IO functionality.
Jakarta Commons Lang: A library that provides various utilities for Java, including some for string manipulation and validation.
Q: How can I contribute to Commons IO?
A: You can contribute to Commons IO by reporting bugs, suggesting improvements, submitting patches, writing documentation, or joining the mailing list. You can find more information on how to contribute on the official website.
Q: How can I learn more about Commons IO?
A: You can learn more about Commons IO by reading the official documentation, browsing the source code[^5^ ], or following the tutorials and examples online.
Q: Where can I get support for Commons IO?
A: You can get support for Commons IO by joining the user mailing list, posting questions on Stack Overflow, or contacting the developers directly. You can find more information on how to get support on the official website. 44f88ac181
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