The 2D Graphics Group

The 2D Graphics group is centered around people interested in the creation and maintenance of the 2D API and implementation.


The Java 2D API and its implementation is often not easily separable from other parts of the Java platform.

Generally it implements geometry, text and image APIs and renders these to screen and printer devices using software, or hardware accelerated means, depending on implementation and/or application or user specified system properties.

Very briefly, the core of the API is the class java.awt.Graphics2D. It provides methods for the rendering operations, as well as controlling the state of the Graphics instance.

There's a large supporting cast of classes in the packages

Image I/O provides the means to load and save sampled images where the in-process image use Java2D's image format.

javax.print is tightly integrated with the java.awt.print package which is the 2D API for rendering to printer graphics devices.

Group policies.

Source code conventions

All source code should follow the standard Java source code conventions as well as jcheck rules. Some of the most common ones to remember are : Consult Code Conventions for the Java(TM) Programming Language for the full list.

Regression tests

Tests should be provided unless clearly infeasible. Automated tests are desirable. SQE rarely run manual tests. Don't give up easily. There are tests that render to a BufferedImage and analyse the resulting contents to see if they behaved correctly, so writing automated tests is possible in more cases than immediately apparent.

Code Reviews

Code reviews are one of the most important mechanisms we have for integrating and shipping good, solid, compatible code. Reviews are also an invaluable source of education for all of us, and a great mechanism for ensuring consistent code quality, as we all read and learn from reading each other's code.

The standard requirement in Java SE is for one (or more) reviewer prior to code freeze and two (or more) reviewers thereafter. The Java client groups have standardized on two reviewers at all times with few exceptions.

The choice of which people review the code is up to the individual engineer and depends upon each specific situation, but some general guidelines are:

It is the responsibility of the implementing engineer to contact the reviewers, respond to their concerns, and make the final code adhere to changes agreed upon by the engineer and the reviewers.

It is the responsibility of the reviewers to provide timely reviews, and understand (to the extent possible) and agree to the changes that the engineer has implemented; when the code is putback to the workspace, the reviewers are also taking responsibility for these changes. We can only have good reviews, and good resulting code, if the reviewers take their jobs seriously and review the changes thoroughly. Given the costs and hassles of maintaining backward-compatible code indefinitely, we cannot risk code going in that is only cursorily reviewed; it is far easier and cheaper to catch flaws in the review process than it is to fix them in bugs and escalations later on.

The most common exceptions to the two reviewer policy would be for

The general process for reviews is as follows:

Regarding Java 2D's source code.

All of Java 2D's code is in the "java.desktop" module, so all references below are relative to the root of the "java.desktop" module.

Aside from the information below developers may find it useful to consult Distinguishing 2D and AWT source files..

Most of the relevant sources have a java and native component.

Most of 2D's code is in 'share'. There is a still significant but lesser amount of code that is specific to X11 or Win32/GDI or macOS. But here for brevity we just point out the shared locations.

These all are under "share". The Java classes are located corresponding to the package hierarchy. E.g. java.awt.Graphics2D is in:

Implementation (non-public) classes are generally in a package starting with "sun.". E.g.:

There are exceptions, notably:

Java 2D also has a substantial amount of native code. This is organised by the shared library into which it is compiled:

(Note that the platform-specific native code is in a corresponding [platform]/native/.. directory)

The shared code location contains essentially complete implementations of everything since 2D has its own code for everything needed to implement the API.

The relevant java.desktop make files found in make/modules/java.desktop.

A more fine grained break down of 2D files, particularly versus AWT component files, can be found here.