NonStop Server for Java 6.0 Programmer's Reference

4 Implementation Specifics
This section explains these subjects regarding HP implementations of NonStop Server for Java,
based on Java Platform Standard Edition 6.0, for Integrity NonStop systems:
• “Headless Support” (page 42)
• “Additional Files” (page 43)
• “Additional Environment Variable” (page 43)
• “Java Native Interface (JNI)” (page 43)
• “IEEE Floating-Point Implementation” (page 46)
• “Multithreaded Programming” (page 47)
• “Java Print Service (JPS)” (page 51)
• “Using the Guardian Printer” (page 51)
• “ThreadDumpPath Support” (page 52)
• “Java Authentication and Authorization Service (JAAS)” (page 53)
• “JavaBeans” (page 53)
• “Debugging Java Programs” (page 54)
• “Deviations in JVM Specification Options” (page 58)
• “Garbage Collection (GC)” (page 59)
• “Java Garbage Collector Tuning for Application Performance” (page 62)
• “Java GC Profiling” (page 64)
• “JVM Tuning Tools” (page 66)
• “Tuning Application Performance” (page 66)
• “Java Signal Handlers” (page 69)
• “Oracle’s Implementation” (page 79)
• “Change in Loading of .hotspot_compiler and .hotspotrc files” (page 70)
In addition, see “Application Profiling” (page 76).
Headless Support
Because the HP NonStop operating system does not provide support for windowing operations,
NonStop Server for Java 6.0 is a headless JVM that conforms to the Sun Microsystems headless
support standard regarding Java Abstract Window Toolkit (AWT) classes and methods. For similar
reasons, the NonStop Server for Java 6.0 does not support the AppletViewer tool.
If your Java programs use classes and methods that require a display, keyboard, sound, or mouse
operation, the class or method will throw a HeadlessException if invoked when
GraphicsEnvironment.isHeadless returns true. This value is always true in NonStop Server
for Java 6.0.
Classes and methods that support printing, fonts, and imaging are fully supported in a headless
JVM.
While the Sun Microsystems documentation for the reference implementation states that you must
set the system property –Djava.awt.headless=true to run a headless JVM, setting this system
property is unnecessary for NonStop Server for Java 6.0.
42 Implementation Specifics