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Guide to GNU gcj

10.14.2 Example

The following code demonstrates the use of the invocation API. In this example, the C++ application initializes the Java runtime and attaches itself. The java.lang.System class is initialized in order to access its out field, and a Java string is printed. Finally, the thread is detached from the runtime once it has finished making Java calls. Everything is wrapped with a try/catch block to provide a default handler for any uncaught exceptions.

The example can be compiled with c++ test.cc -lgcj.

// test.cc #include <gcj/cni.h> #include <java/lang/System.h> #include <java/io/PrintStream.h> #include <java/lang/Throwable.h> int main(int argc, char *argv) { using namespace java::lang; try { JvCreateJavaVM(NULL); JvAttachCurrentThread(NULL, NULL); String *message = JvNewStringLatin1("Hello from C++"); JvInitClass(&System.class$); System::out->println(message); JvDetachCurrentThread(); } catch (Throwable *t) { System::err->println(JvNewStringLatin1("Unhandled Java exception:")); t->printStackTrace(); } }