What is a library?
A library is a set of commands, classes, and/or data types that help extend the functionality of your code. You can use certain libraries to shorten a task in java or to add on extra features to your programming experience. These libraries can be called at runtime when the program is running.
Some popular libraries include ones that we already went over. Java.util .* has some popular features such as the ArrayList capability for resizable arrays, and the Scanner function for user input. Other ones include java.io which is used to read and edit any type of file. There is Java.math which adds significant capabilities to programming with math. Javax is popularly used to make applications with GUI. There are many more java libraries and extensions to learn.