Java graphics without X server

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A frequently asked question in the context of loading images with Java—or, more broadly, doing any image manipulation with Java's built-in classes—is that of the missing X server. Unix users who just want to load an image via the AWT without displaying it get an error message if there is no X server installed (which is true for many server systems). In fact, by default the X server is required for that. Here are some tips on how to solve that problem:

Use PJA (Pure Java AWT).
Install xvfb: “It provides an X server that can run on machines with no display hardware and no physical input devices. It emulates a dumb framebuffer using virtual memory.”
Use Java 1.4 or higher, which supports headless Java (no more X server required). Run your application with -Djava.awt.headless=true given as parameter to the virtual machine. Java 1.4 also includes an image I/O API that reportedly does not require an X server.
Java imaging libraries which do not rely on Java's own imaging functionality can be a solution. However, while I offer a list of imaging libraries, I have not checked them for that particular property.

Note that Java Advanced Imaging does not need an X server for loading GIFs and JPEGs since version 1.1.1.

Davisor Ltd. who offer a commercial Java chart library also have some tips related to this problem.