Java application notes

API docs

Java API documentation is maintained with Javadoc. To build the documentation, build LCM and then run the script:

$ lcm-java/

Finding lcm.jar

The core LCM Java implementation is built to lcm.jar. To use LCM in your application, lcm.jar must be in your Java classpath.

On Linux, OS/X, and other UNIX-like systems, lcm.jar is typically built automatically and installed along with the rest of LCM. The exact location depends on the operating system and any configuration parameters, but it can often be found installed in /usr/local/share/java/.

Separately, lcm.jar can also be found in the lcm-java subdirectory of the source distribution after compiling LCM from source.

Building lcm.jar separately from the rest of LCM

It is possible to build lcm.jar separately from the rest of LCM. The lcm-java subdirectory of the source distribution contains a build.xml file, which can be used with a build tool like Apache Ant or Eclipse.

Namespace issues

LCM supports namespaces for data types, making it easier for users to use the types defined by others without worry that those types will conflict with other users' types.

When defining a type, the name of the type can include a namespace, e.g., "struct examples.temperature_t { ... }". When compiled with lcm-gen, this will result in a class named "temperature_t" in package "examples". If lcm-gen is given the root of a source tree with the –jpath flag, it will automatically put temperature_t.class in the examples subdirectory. You will need to remember to import that type before you use it, e.g., "import examples.*", or else you will need to refer to types by their fully-qualified names (e.g., "new examples.temperature_t()").

Note that if you do not specify a package name in your LCM type definition file, lcm-gen will (by default) put those types into the "lcmtypes" Java package. This is necessary because Java does not officially support packageless classes.