Chapter 2: ClassUtils

The ClassUtils utility stands out as an essential tool for developers utilizing reflection in Java. It simplifies interactions with classes and interfaces, allowing for easier manipulation without the intricacies of Java's reflection APIs. However, it is worth noting that this utility may not be ideal for performance-critical applications.

Example:

import org.apache.commons.lang3.ClassUtils;

public class ClassUtilsExample {

public static void main(String[] args) {

// Retrieve all interfaces implemented by ArrayList

System.out.println(ClassUtils.getAllInterfaces(ArrayList.class));

// Get the canonical name of the class

System.out.println(ClassUtils.getCanonicalName(ArrayList.class));

// Verify if the specified class can be cast to a reference class

System.out.println(ClassUtils.isAssignable(ArrayList.class, List.class));

}

}

Chapter 3: ExceptionUtils

Managing exceptions is a vital aspect of programming, but traditional Java practices can be tedious. ExceptionUtils offers helpful tools for effectively handling exceptions, including methods for extracting the root cause or obtaining the stack trace as a string.

Example:

import org.apache.commons.lang3.exception.ExceptionUtils;

public class ExceptionUtilsExample {

public static void main(String[] args) {

try {

// Code that may throw an exception

} catch (Exception e) {

// Retrieve the root cause of the exception

Throwable rootCause = ExceptionUtils.getRootCause(e);

System.out.println(rootCause);

// Obtain the stack trace as a string

String stackTrace = ExceptionUtils.getStackTrace(e);

System.out.println(stackTrace);

}

}

}

Chapter 4: EnumUtils

Enums are frequently used in Java, yet handling them can sometimes be cumbersome. EnumUtils aids in enum operations, such as listing all enum constants, checking for specific names, or converting a string into an enum.

Example:

import org.apache.commons.lang3.EnumUtils;

public enum Status {

PENDING, PROCESSING, COMPLETED

}

public class EnumUtilsExample {

public static void main(String[] args) {

// Validate if the enum contains a specific name

System.out.println(EnumUtils.isValidEnum(Status.class, "PENDING"));

// Retrieve the enum list

System.out.println(EnumUtils.getEnumList(Status.class));

// Convert a string to an enum

Status status = EnumUtils.getEnum(Status.class, "COMPLETED");

System.out.println(status);

}

}

Chapter 5: DurationFormatUtils

Calculating and formatting time can be complex in Java. DurationFormatUtils makes this easier by offering methods for formatting durations into a human-readable format.

Example:

import org.apache.commons.lang3.time.DurationFormatUtils;

public class DurationFormatUtilsExample {

public static void main(String[] args) {

long durationMillis = 120000; // 2 minutes in milliseconds

// Format duration in H:m:s.S format

String formattedDuration = DurationFormatUtils.formatDuration(durationMillis, "H:mm:ss.S");

System.out.println(formattedDuration);

// Format duration in words

String formattedDurationWords = DurationFormatUtils.formatDurationWords(durationMillis, true, true);

System.out.println(formattedDurationWords);

}

}

Chapter 6: IOUtils

Input/output operations are fundamental to any Java application. IOUtils provides a suite of utilities to facilitate these tasks, such as reading from a stream, writing to a stream, copying between streams, and closing streams quietly, reducing verbosity and error-prone code associated with standard Java I/O.

Example:

import org.apache.commons.io.IOUtils;

import java.io.InputStream;

import java.io.StringWriter;

import java.nio.charset.StandardCharsets;

public class IOUtilsExample {

public static void main(String[] args) {

InputStream input = null;

StringWriter writer = new StringWriter();

try {

// Typically obtained from a file, URL, or socket

input = IOUtilsExample.class.getResourceAsStream("/example.txt");

// Use IOUtils to copy the InputStream into a StringWriter

IOUtils.copy(input, writer, StandardCharsets.UTF_8);

// The content of the InputStream as a String

String theString = writer.toString();

System.out.println(theString);

} catch (Exception e) {

e.printStackTrace();

} finally {

// Close the stream quietly without throwing an exception

IOUtils.closeQuietly(input);

IOUtils.closeQuietly(writer);

}

}

}

In this example, the IOUtils.copy() method transfers the contents of an InputStream to a StringWriter, streamlining data reading. Additionally, IOUtils.closeQuietly() effectively closes streams without raising an IOException, leading to cleaner code when managing stream closures.