Introduction to Apache Commons Lang

The Apache Commons Lang library is a popular set of utility classes that make working with core Java features easier and more efficient. It focuses on simplifying everyday programming tasks that you often encounter when working with Java's standard libraries.

Apache Commons Lang is especially useful when you need to:

• Manipulate and format strings;
• Work with numbers and mathematical operations;
• Handle objects, arrays, and reflection safely;
• Simplify tasks like building toString() methods, comparing objects, or checking for null values.

Java's built-in libraries provide powerful features, but they sometimes require extra code for common tasks. Apache Commons Lang fills these gaps by offering ready-made solutions, saving you time and reducing errors. By using this library, you can write cleaner, more reliable code with less effort.

Common Classes and Methods in Apache Commons Lang

Apache Commons Lang provides a set of helpful utility classes that make working with core Java types easier and more reliable. Here are some of the most commonly used classes:

StringUtils

StringUtils offers methods for manipulating and checking strings, helping you avoid common errors like NullPointerException and making code more readable.

• Check if a string is empty or blank with StringUtils.isEmpty() and StringUtils.isBlank();
• Join an array or list of strings into a single string using StringUtils.join();
• Reverse a string with StringUtils.reverse();
• Remove whitespace from the start and end of a string using StringUtils.trim().

Example:

String name = null;
boolean isNameEmpty = StringUtils.isEmpty(name); // true
String joined = StringUtils.join(new String[]{"Java", "Lang"}, "-"); // "Java-Lang"

ObjectUtils

ObjectUtils helps you work with objects safely, especially when dealing with null values.

• Return a default value if an object is null using ObjectUtils.defaultIfNull();
• Compare objects safely with ObjectUtils.equals();
• Get the first non-null value from multiple options using ObjectUtils.firstNonNull().

Example:

String value = null;
String safeValue = ObjectUtils.defaultIfNull(value, "default"); // "default"

ArrayUtils

ArrayUtils provides methods for working with arrays, making tasks like searching, adding, or removing elements much easier.

• Check if an array is empty with ArrayUtils.isEmpty();
• Add an element to an array using ArrayUtils.add();
• Remove an element from an array with ArrayUtils.remove();
• Find the index of an element using ArrayUtils.indexOf().

Example:

int[] numbers = {1, 2, 3};
int[] newNumbers = ArrayUtils.add(numbers, 4); // {1, 2, 3, 4}
boolean empty = ArrayUtils.isEmpty(new int[]{}); // true

These utility classes save you time and help you write safer, more readable code when working with strings, objects, and arrays.