How do I calculate directory size?

By I Wayan Saryada 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 I Wayan Saryada 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 I Wayan Saryada 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 convert an array of primitives into an array of objects?

By I Wayan Saryada in Apache Commons, Commons Lang 0 Comment

To convert from primitive arrays into object type arrays, we can use the Apache Commons Lang library. The Commons Lang provides an ArrayUtils class that does this conversion. To convert the other way just use the toPrimitive() method.

package org.kodejava.commons.lang;

import org.apache.commons.lang3.ArrayUtils;

public class ArrayPrimitiveObjectConversionDemo {
    public static void main(String[] args) {
        int[] numbers = {1, 2, 3, 4, 5};
        boolean[] booleans = {true, false, false, true};
        float[] decimals = {10.1f, 3.14f, 2.17f};

        Integer[] numbersObjects = ArrayUtils.toObject(numbers);
        Boolean[] booleansObjects = ArrayUtils.toObject(booleans);
        Float[] decimalsObjects = ArrayUtils.toObject(decimals);

        numbers = ArrayUtils.toPrimitive(numbersObjects);
        booleans = ArrayUtils.toPrimitive(booleansObjects);
        decimals = ArrayUtils.toPrimitive(decimalsObjects);
    }
}

Maven Dependencies

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.14.0</version>
</dependency>

Maven Central

How do I use Apache Commons Lang ToStringBuilder class?

By I Wayan Saryada in Apache Commons, Commons Lang 0 Comment

The toString() method defined in the java.lang.Object can be overridden when we want to give more meaningful information about our object. We can simply return any information of the object in the toString() method, for instance the value of object’s states or fields.

The Apache Commons Lang library offers a good utility for creating this toString() information. Here I give a simple example using the ToStringBuilder class.

package org.kodejava.commons.lang;

import org.apache.commons.lang3.builder.ToStringBuilder;
import org.apache.commons.lang3.builder.ToStringStyle;

public class ToStringBuilderDemo {
    private Long id;
    private String firstName;
    private String lastName;

    public static void main(String[] args) {
        ToStringBuilderDemo demo = new ToStringBuilderDemo();
        demo.id = 1L;
        demo.firstName = "First Name";
        demo.lastName = "Last Name";

        System.out.println(demo);
    }

    public String toString() {
        return new ToStringBuilder(this, ToStringStyle.MULTI_LINE_STYLE)
            .append("id", id)
            .append("firstName", firstName)
            .append("lastName", lastName)
            .toString();
    }
}

The ToStringStyle class allows us to choose the styling for our toString() method when we print it out. Here are the available styles that we can use.

  • ToStringStyle.DEFAULT_STYLE
  • ToStringStyle.JSON_STYLE
  • ToStringStyle.MULTI_LINE_STYLE
  • ToStringStyle.NO_CLASS_NAME_STYLE
  • ToStringStyle.NO_FIELD_NAMES_STYLE
  • ToStringStyle.SHORT_PREFIX_STYLE
  • ToStringStyle.SIMPLE_STYLE

The result of the code above is:

org.kodejava.commons.lang.ToStringBuilderDemo@8efb846[
  id=1
  firstName=First Name
  lastName=Last Name
]

Below are example results of the other ToStringStyle:

  • ToStringStyle.DEFAULT_STYLE
org.kodejava.commons.lang.ToStringBuilderDemo@d716361[id=1,firstName=First Name,lastName=Last Name]
  • ToStringStyle.JSON_STYLE
{"id":1,"firstName":"First Name","lastName":"Last Name"}
  • ToStringStyle.NO_CLASS_NAME_STYLE
[id=1,firstName=First Name,lastName=Last Name]
  • ToStringStyle.NO_FIELD_NAMES_STYLE
org.kodejava.commons.lang.ToStringBuilderDemo@d716361[1,First Name,Last Name]
  • ToStringStyle.SHORT_PREFIX_STYLE
ToStringBuilderDemo[id=1,firstName=First Name,lastName=Last Name]
  • ToStringStyle.SIMPLE_STYLE
1,First Name,Last Name

If you want to make the code event more simple by using the ToStringBuilder.reflectionToString() method to generate the string for the toString() method to return. Using this method the ToStringBuilder will the hard job of finding information about our class and return the string information.

Maven Dependencies

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.14.0</version>
</dependency>

Maven Central