Splitting code into files
As your project grows, putting everything in one file becomes a nightmare. Java lets you split code across many files (called modules) and import names from one file into another. Each module groups together a related set of functions and types.
```java
// File: util/Math.java
package util;
public class Math {
public static int add(int a, int b) { return a + b; }
}// File: Main.java import util.Math; System.out.println(Math.add(2, 3)); ```
Third-party packages
You almost never need to write everything from scratch. Java has a huge ecosystem of open-source libraries — for parsing JSON, talking to databases, building web servers, doing maths, and thousands of other tasks. Use the official package manager to add and update dependencies.
Keeping dependencies under control
Each dependency you add is code written by strangers running inside your program. Read what a package actually does before you install it, prefer well-maintained projects with many users, and remove dependencies you no longer use.