1. Creating a Package

Use the package keyword at the very beginning of your Java file (before any class declaration). This statement must be the first line of code in the file.

package mypackage;

public class MyClass {
    // class code here
}

Note: The file must be saved in a folder named mypackage to match the package name.

2. Importing a Package

Use the import keyword to use classes from other packages in your code.

import mypackage.MyClass;

// Or import all classes from a package
import mypackage.*;

Note: The * wildcard imports all classes from the package, but it's better to import only what you need.

Step 1: Create a Package with a Class

Create a file named Calculator.java in a folder named mathtools:

package mathtools;

public class Calculator {
    // Method to add two numbers
    public int add(int a, int b) {
        return a + b;
    }
    
    // Method to subtract two numbers
    public int subtract(int a, int b) {
        return a - b;
    }
    
    // Method to multiply two numbers
    public int multiply(int a, int b) {
        return a * b;
    }
    
    // Method to divide two numbers
    public double divide(int a, int b) {
        if (b != 0) {
            return (double) a / b;
        } else {
            System.out.println("Cannot divide by zero!");
            return 0;
        }
    }
}

Step 2: Use the Package in Another Class

Create a file named Main.java in your main project folder:

import mathtools.Calculator;

public class Main {
    public static void main(String[] args) {
        // Create an object of Calculator class
        Calculator calc = new Calculator();
        
        // Use the methods
        System.out.println("Addition: " + calc.add(10, 5));
        System.out.println("Subtraction: " + calc.subtract(10, 5));
        System.out.println("Multiplication: " + calc.multiply(10, 5));
        System.out.println("Division: " + calc.divide(10, 5));
    }
}

Addition: 15
Subtraction: 5
Multiplication: 50
Division: 2.0

MyProject/
├── Main.java
└── mathtools/
    └── Calculator.java