1. Lists

A List is an ordered collection that allows duplicate elements. It maintains the insertion order, which means the elements are stored in the order they were added. Here’s how you can create a simple List:

2. Sets

A Set is an unordered collection that does not allow duplicate elements. It’s useful when you need to ensure uniqueness. Here’s an example using a HashSet:

3. Maps

A Map is a key-value pair collection. It allows you to associate values with unique keys. The most common implementation is HashMap. Here’s an example:

Java’s Built-In APIs

Java provides a rich set of built-in APIs for various tasks. Here are a few commonly used ones:

java.util.Arrays: Contains utility methods for working with arrays.
java.util.String: Provides methods for string manipulation.
java.util.Math: Includes mathematical functions like sqrt, pow, and random.
Remember to import the necessary packages when using these APIs.