What is the convention for word separator in Java package names?

Rules of Engagement

Navigating Java package name conventions can be akin to negotiating a linguistic minefield. Here are the key conventions:

• Lowercase letters: Using lowercase letters avoids confusion with class names, which typically use CamelCase.
• Dot Separator: Separate components of the package hierarchy using dots.
• No Special Characters: Don't use underscores and hyphens to separate words. If your package name includes domain names with hyphens, replace the hyphen with an underscore.
• Avoid Keywords: If you absolutely must use a Java keyword as part of your package name, prefix or suffix it with an underscore.
• Consider Readability: Your package name should succinctly describe its contents in an easily comprehensible manner.

// Welcome to the Java package lowlands
package com.stackoverflow.this_is_not_the_package_you_are_looking_for;
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Exceptions are NOT exceptional

Even in the world of Java package naming conventions, certain exceptions and idiosyncrasies exist. It's crucial to bear them in mind:

• Special Characters in Domain Names: Is there a hyphen in your domain name? Replace it with an underscore when adopting it as a package name.
• Java Keywords: Dress up Java keywords with an underscore prefix or suffix to prevent conflicts.
• Capital Offenses: Avoid uppercase letters in package names to keep them distinct from class names.
• Domain Name Prefixes: Adopting domain-based prefixes for package names not only mirrors domain ownership but also should be in lowercase to adhere to Java standards.

Code Gymnastics

Here are a few best practices that could steer you through potential package naming storms:

• Tailor-made Guidelines: Sometimes, organizations have unique conventions. As long as these largely comply with Java standards, they're kosher!
• Documentation: Use package-info.java to comment about the package purpose and content — it's like leaving a trail of breadcrumbs for fellow developers!
• Usability Matters: Think about the package consumers - your fellow developers! Is your package name self-explanatory, intuitive even?
• Look & Feel: Balance length against clarity to achieve optimal readability and flow.

Reality Check

For added context, here are real-world examples of Java package naming conventions in the wild:

• Apache Commons Lang: Consistent adherence to Java standards is evident in org.apache.commons.lang3.
• Google's Guava library: The package name com.google.common.collect flows with ease and meets all Java guidelines.

To get a sense of how these principles translate into practice, poke around these libraries!