Packages in Java

Package

A package is a grouping of related types providing access protection and name space management.

Advantages

  • Easy to determine how types are related.
  • Makes sure that your names don’t conflict with the names used in the package.

Creating a package

import mypackage;

Naming Convention

Packages solve the naming problem but what if two programmers create packages with the same name. That’s why we have naming convention for packages.

  • Package names are written in all lowercase.
  • Companies use their reverse domain name to begin their project
    • ex: com.example.package
  • If multiple package with similar name are there in the company then project name can be added to package name.
    • ex: com.example.project.package

Package Members

The types that comprise of a package are called package members.

Fully qualified name

A fully qualified name of a package member is the package name followed by the type you want to access.

com.example.project.mypackage.ClassName

Using package members

Refering using fully qaulified name.

If you have not imported a package than you can access the types defined in that package by using their fully qualified name.

Importing a package member

You can import the specific memebers of a package using import statement.

import com.example.project.mypackage.ClassName;

Now you don’t need to use the fully qualified name to use this package member.

Importing a whole package

You can import the whole package and access all it’s type using simple names instead of full qualified names.

import com.example.project.mypackage.*;

For convinience complier automatically imports two packages for all source files java.lang and the current package.

All Classes and variables by default have package scope if we don’t use public or private.