How do I calculate directory size?

By Wayan in Apache Commons, Commons IO 0 Comment

In this example, we are going to use the Apache Commons IO library to get or calculate the total size of a directory. The FileUtils class provided by the Commons IO can help us to achieve this goal.

The first method that we can use is the FileUtils.sizeOfDirectory(), it calculates the size of a directory recursively. It takes a File object that represent a directory as parameter and returns long value. If the directory has security restriction this method return 0. A negative value returned when the directory size if bigger than Long.MAX_VALUE.

You can also use the FileUtils.sizeOfDirectoryAsBigInteger() method. This method returns the result as BigInteger as the method name describe. As the first method, this method also return 0 when the directory has a security restriction.

Both of the methods described above return the directory size in byte. If you want a more human-readable size you can utilize the FileUtils.byteCountToDisplaySize() method, it will convert the byte value into something like 1 MB, 1 GB.

package org.kodejava.commons.io;

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.math.BigInteger;

public class DirectorySizeSample {
    public static void main(String[] args) {
        // sizeOfDirectory
        File tempDir = new File("/Users/wayan/Temp");
        long size = FileUtils.sizeOfDirectory(tempDir);
        System.out.println("TempDir size = " + size + " bytes");
        System.out.println("TempDir size = " +
                FileUtils.byteCountToDisplaySize(size));

        // sizeOfDirectoryAsBigInteger()
        File dropboxDir = new File("/Users/wayan/Dropbox");
        BigInteger sizeBig = FileUtils.sizeOfDirectoryAsBigInteger(dropboxDir);
        System.out.println("DropboxDir size = " + sizeBig);
        System.out.println("DropboxDir size = " +
                FileUtils.byteCountToDisplaySize(sizeBig));
    }
}

The result of the code snippet above:

TempDir size = 514239345 bytes
TempDir size = 490 MB
DropboxDir size = 6184
DropboxDir size = 6 KB

Maven Dependencies

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.14.0</version>
</dependency>

Maven Central

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 2 Comments

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>2.14.0</version>
</dependency>

Maven Central

How do I read file contents to string using Commons IO?

By Wayan in Apache Commons, Commons IO 0 Comment

In this example we use FileUtils class from Apache Commons IO to read the content of a file. FileUtils have two static methods called readFileToString(File) and readFileToString(File, String) that we can use.

An example to read file contents and return the result as a string can be seen below.

package org.kodejava.commons.io;

import org.apache.commons.io.FileUtils;

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

public class ReadFileToStringSample {
    public static void main(String[] args) {
        // Here we create an instance of File for sample.txt file.
        File file = new File("sample.txt");

        try {
            // Read the entire contents of sample.txt
            String content = FileUtils.readFileToString(file, "UTF-8");
            System.out.println("File content: " + content);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.14.0</version>
</dependency>

Maven Central

How do I read entries in a zip / compressed file?

By Wayan in Zip and GZIP 0 Comment 
package org.kodejava.util.zip;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Enumeration;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;

public class ZipFileExample {
    public static void main(String[] args) {
        try {
            // Create an instance of ZipFile to read a zip file
            // called sample.zip
            ZipFile zip = new ZipFile(new File("data.zip"));

            // Here we start to iterate each entry inside
            // sample.zip
            for (Enumeration<?> e = zip.entries(); e.hasMoreElements(); ) {
                // Get ZipEntry which is a file or a directory
                ZipEntry entry = (ZipEntry) e.nextElement();

                // Get some information about the entry such as
                // file name, its size.
                System.out.println("File name: " + entry.getName()
                    + "; size: " + entry.getSize()
                    + "; compressed size: "
                    + entry.getCompressedSize());
                System.out.println();

                // Now we want to get the content of this entry.
                // Get the InputStream, we read through the input
                // stream until all the content is read.
                InputStream is = zip.getInputStream(entry);
                InputStreamReader isr = new InputStreamReader(is);

                char[] buffer = new char[1024];
                while (isr.read(buffer, 0, buffer.length) != -1) {
                    String s = new String(buffer);
                    // Here we just print out what is inside the
                    // buffer.
                    System.out.println(s.trim());
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

What is Autoboxing?

By Wayan in Basic, Core API 0 Comment

Autoboxing is a new feature offered in the Tiger (1.5) release of Java SDK. In short auto boxing is a capability to convert or cast between object wrappers (Integer, Long, etc) and their primitive types.

Previously when placing primitive data into one of the Java Collection Framework object we have to wrap it to an object because the collection cannot work with primitive data. Also, when calling a method that requires an instance of object rather than an int or long, we have to convert it too.

Now, starting from version Java 1.5 we have a new feature in the Java Language which automate this process, its call the Autoboxing. When we place an int value into a collection, such as List, it will be converted into an Integer object behind the scene. When we read it back, it will automatically convert to the primitive type. In most way this simplifies the way we code, no need to do an explicit object casting.

Here an example how it will look like using the Autoboxing feature:

package org.kodejava.basic;

import java.util.HashMap;
import java.util.Map;

public class Autoboxing {
    public static void main(String[] args) {
        Map<String, Integer> map = new HashMap<>();

        // Here we put an int into the Map, and it accepted
        // as it will be autoboxed or converted into the wrapper
        // of this type, in this case the Integer object.
        map.put("Age", 25);

        // Here we can just get the value from the map, no need
        // to cast it from Integer to int.
        int age = map.get("Age");

        // Here we simply do the math on the primitive type
        // and got the result as an Integer.
        Integer newAge = age + 10;
    }
}