Wego Engineering

Java style guide for Wego

Everyone has an opinion on how to write Java. Here's ours and remember

• 80% of the lifetime cost of a piece of software goes to maintenance.
• Hardly any software is maintained for its whole life by the original author.
• Code conventions improve the readability of the software, allowing engineers to understand new code more quickly and thoroughly.

We highly advise the developer to use Eclipse when developing Java apps. You need to download the latest Eclipse IDE. Please be sure to configure the following in your Eclipse instance:

• Adjust your Eclipse setting to format your code upon save. To do so, go to Preferences > Java > Editor > Save Action and tick Format source code then Format all lines and Organize imports.
• Remove all trailing white spaces upon Save. Go to Preferences > Java > Editor > Save Action and tick Additional actions and click on Configure... and tick Remove trailing whitespace then All lines and Correct indentation.

Naming

• Use camelCase when naming objects, functions, and instances.
• Use PascalCase when naming constructors or classes.
• Use NAMES_LIKE_THIS for constant values.

Standard libraries

• Must use Apache Common instead JDK, i.e. StringUtils.equals StringUtils.split. JDK's String related functions are not null-safe.
• Must use Guava instead of JDK, i.e. ThreadFactoryBuilder Cache Ordering Maps ImmutableMap ListenableFuture.
• Must use Joda instead of JDK, i.e. DateTime Duration Period DateTimeFormatter. JDK's Date SimpleDateFormat are not thread-safe.
• Must use Jackson JSON to deserialize objects into JSON, and use mixin annotation. Java default serializer is known to be very slow.

Other notes

• Always use logger and do not use System.out for logging. Additionally, when doing logging, always enclose your debug messages with a checker to determine whether debug has been enabled. Logging can cause performace issues. With this practice, we can reduce the effects of logging by changing log level.

  // bad
  logger.debug("This is a " + message)
  
  // good
  if (logger.isDebugEnabled()) {
      logger.debug("This is a {}", message);
  }
  
  if (logger.isTraceEnabled()) {
      logger.trace("This is a {}", message);
  }
  

• Always use braces after your if else for while even in the case you need to run one line of code. This is to reduce the errors when you do refactoring code in the future.

  // bad
  if (StringUtils.equals(result, "bad"))
      bad();
  else
      veryBad();
  
  // good
  if (StringUtils.equals(result, "good")) {
      good();
  } else {
      veryGood();
  }
  

• Do not create static String unless you want to share them between functions. In-code strings are already cached in a pool by JVM.

• Create thread-safe objects and re-use them instead of creating new object everytime in a function or in a for loop.

• Name your theads and make them daemon when you need to create a thread pool. This makes debugging easier and removes blocking in the main thread when it needs to quit.

  Executors.newCachedThreadPool(new ThreadFactoryBuilder()
      .setDaemon(true)
      .setNameFormat("some-fancy-theads-%s")
      .build());
  

For more guidelines, please follow closely Oracle's Coding Convention.