Java code for the Geode project was originally developed using conventions based on The Elements of Java Style, by A. Vermeulen, S. Ambler, et. al.

As an open-source project we are following the Google Java Style guide, emphasizing a few of the more important points in this page.

General Principles

When modifying existing software, your changes should follow the style of the original code. Do not introduce a new coding style in a modification, and do not attempt to rewrite the old software just to make it match the new style. The use of different styles within a single source file produces code that is more difficult to read and comprehend. Rewriting old code simply to change its style may result in the introduction of costly yet avoidable defects.

Apply these rules to any code you write, not just code destined for production or only if it is visible to the user. This includes code documentation (javadocs).

Formatting Conventions

In order to create a source base that has a unified appearance and is easy to read and comprehend we include conventions for formatting Java code.

Most of the formatting conventions for this project center around the use of white space and the placement of brackets. Formatter settings for Eclipse and IntelliJ are covered first, followed by more detailed descriptions.

File encoding

Use UTF-8 file encoding and Unix line separators. Some source code files contain UTF-8 characters and will be damaged if you modify them with an editor that does not support UTF-8 encoding.

Line Length

Limit your source code line length to 100 characters.

Indentation

Improve code readability by grouping individual statements into block statements and uniformly indent the content of each block to set off its contents from the surrounding code.

...

Use 2-space indentation in general.

Curly Braces

Always use braces, even around one-line `if`, `else` and other control statements.

...

    // CORRECT: A public class definition
    public class MyClass {
      ...
    }

    // WRONG:
    public class MyClass
    {
      ...
    }

    // WRONG:
    public class MyClass {
      ...
      }

    // CORRECT: A method definition
    void method(int j) {
      ...
    }
    
    // CORRECT: A do/while
    do {
      ...
    } while (...)

...

Eclipse and IntelliJ formatter settings

Eclipse

On MacOS "Preferences..." can be found under the "Eclipse" menu.

...

Avoid using auto-formatting - "Ctrl + Shift + F" for an entire file while changing a part of the file. Especially for an existing file as it makes it difficult to know the exact difference by comparing revisions.

IntelliJ

Open the Settings dialog with File -> Settings...

...

Avoid using reformatting commands for an entire file while changing a part of the file. Especially for an existing file as it makes it difficult to know the exact difference by comparing revisions.

Patterns

Line Separator

Use java.lang.System.lineSeparator() instead of java.lang.System.getProperty("line.separator").

Serializable Types

Use of java.io.Serializable should be avoided unless absolutely necessary for integration with 3rd party libraries. Any type that is to be serialized to persistent storage or over the Geode network protocols should implement one of Geode's alternative serialization methods, SerializableFixedID, DataSerializable, etc.