How do I read text file content line by line to a List of Strings using Commons IO?

By Wayan in Apache Commons, Commons IO 0 Comment

The following example show how to use the Apache Commons IO library to read a text file line by line to a List of String. In the code snippet below we will read the contents of a file called sample.txt using FileUtils class. We use FileUtils.readLines() method to read the contents line by line and return the result as a List of Strings.

package org.kodejava.commons.io;

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;
import java.util.List;

public class ReadFileToListSample {
    public static void main(String[] args) {
        // Create a file object of sample.txt
        File file = new File("README.md");

        try {
            List<String> contents = FileUtils.readLines(file, "UTF-8");

            // Iterate the result to print each line of the file.
            for (String line : contents) {
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.16.1</version>
</dependency>

Maven Central

How do I create a java.io.File object from URL?

By Wayan in Apache Commons, Commons IO 0 Comment

The code snippet below uses the FileUtils.toFile(URL) method that can be found in the Apache Commons IO library to convert a URL into a File. The url protocol should be file or else null will be returned.

package org.kodejava.commons.io;

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.net.URI;
import java.nio.charset.StandardCharsets;
import java.util.Objects;

public class URLToFileObject {
    public static void main(String[] args) throws Exception {
        // FileUtils.toFile(URL url) convert from URL the File.
        String data = FileUtils.readFileToString(Objects.requireNonNull(
                        FileUtils.toFile(URLToFileObject.class.getResource("/data.txt"))),
                StandardCharsets.UTF_8);
        System.out.println("data = " + data);

        // Creates a URL with file protocol and convert it into File object.
        File file = FileUtils.toFile(URI.create("file:///D:/data.txt").toURL());
        data = FileUtils.readFileToString(file, StandardCharsets.UTF_8);
        System.out.println("data = " + data);
    }
}

Maven Dependencies

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.16.1</version>
</dependency>

Maven Central

How do I move directory to another directory with its entire contents?

By Wayan in Apache Commons, Commons IO 3 Comments

Below is an example to move one directory with all its child directory and files to another directory. We can use the FileUtils.moveDirectory() method to simplify the process.

package org.kodejava.commons.io;

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;

public class DirectoryMove {
    public static void main(String[] args) {
        String source = "F:/Temp/source";
        File srcDir = new File(source);

        String destination = "F:/Temp/target";
        File destDir = new File(destination);

        try {
            // Move the source directory to the destination directory.
            // The destination directory must not exist prior to the
            // move process.
            FileUtils.moveDirectory(srcDir, destDir);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.16.1</version>
</dependency>

Maven Central

How do I copy directory with all its contents to another directory?

By Wayan in Apache Commons, Commons IO 0 Comment

To copy a directory with the entire child directories and files we can use a handy method provided by the Apache Commons IO FileUtils.copyDirectory(). This method accepts two parameters, the source directory and the destination directory. The source directory should be available while if the destination directory doesn’t exist, it will be created.

package org.kodejava.commons.io;

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;

public class DirectoryCopy {
    public static void main(String[] args) {
        // An existing directory to copy.
        String source = "F:/Temp/source";
        File srcDir = new File(source);

        // The destination directory to copy to. This directory
        // doesn't exist and will be created during the copy
        // directory process.
        String destination = "F:/Temp/target";
        File destDir = new File(destination);

        try {
            // Copy source directory into destination directory
            // including its child directories and files. The
            // destination directory will be created if it does
            // not exist. This copy processes also preserve the
            // date information of the file.
            FileUtils.copyDirectory(srcDir, destDir);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.16.1</version>
</dependency>

Maven Central

How do I copy a URL into a file?

By Wayan in Apache Commons, Commons IO 6 Comments

The code snippet below shows you how to use the FileUtils.copyURLToFile(URL, File) method of the Apache Commons IO library to help you to copy the contents of a URL directly into a file.

package org.kodejava.commons.io;

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;
import java.net.URI;
import java.net.URL;

public class URLToFile {
    public static void main(String[] args) {
        try {
            URL url = URI.create("https://www.google.com").toURL();
            File destination = new File("google.html");

            // Copy bytes from the URL to the destination file.
            FileUtils.copyURLToFile(url, destination);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.16.1</version>
</dependency>

Maven Central