Package, import

A package contains Java code. It has classes, methods, and other forms of data. We import a package to use it in our program.

To begin, please create a new Java package. Call it something like testPackage and then place a public method in the class. The file declares itself as a package with the package keyword.

Code example

Here we see our testPackage package. It contains a class called Test and a printName method. These projects are in the same directory in Eclipse.

package testPackage;

public class Test {

    public void printName() {
        // This method is in the Test class in testPackage.
        System.out.println("Dot Net Perls");
    }
}
import testPackage.Test;

public class Program {
    public static void main(String[] args) {

        // Create new instance of Test from testPackage.
        Test test = new Test();
        // Call method.
        test.printName();
    }
}
Dot Net Perls

Star

With a star, we can import all types in a certain package. Consider the java.util.function package. We can import all its classes with a star directive.

import java.util.function.*;

Package and import

We created a package and imported it into the default package. Importing a package simply makes it easier to access—we can use the "Test" class directly.

With the import keyword, we can use classes like ArrayList with simpler syntax. For ArrayList we import java.util.ArrayList. This makes programs easier to read.

Modularity is a key part of Java programming. Object-oriented programming is about decomposing programs into small parts that can be reused. Packages are meant to be used again and again.