Here is a sample project demonstrating the basics of building a CNI
application with GCJ version 3.0.  Note that the 'sampSTL' gyrations
are necessary only if you use code within your CNI methods that
could conceivably catch a C++ exception.

It assumes that you have installed the binaries in a directory
in your path.

==> Makefile <==
sample:  sample.o sampNat.o sampSTL.o
	gcj -o sample \
		sample.o sampNat.o sampSTL.o -lstdc++ --main=sample

sample.o:  sample.class
	gcj -c sample.class

sample.class: sample.java
	gcj -C sample.java

sample.h: sample.class
	gcjh sample

sampNat.o: sample.h sampNat.cc
	g++ -c sampNat.cc

clean:
	rm -f sample sample.o sampNat.o sampSTL.o sample.class sample.h

==> sampNat.cc <==
#include <gcj/cni.h>
#include "sample.h"
//#include <stream.h>
#include <java/io/PrintStream.h>
#include <java/lang/System.h>
#include <java/lang/String.h>

void sample::myNative(java::lang::String *s)
{
  // Due to the new exception-handling code implemented
  // in gcc version 3.0, the following line will fail
  // with an error about mixing exception types between
  // C++ and Java.  Factoring this code out into a
  // seperate function that does not include any Java
  // code solves the problem.
  //  cout << "Hello, C++" << endl;
  callSTLcode();

  // In version 2.96, the following line causes a link error 
  // for a missing typeinfo unless this file is compiled 
  // with '-fno-rtti'.  This is corrected in version 3.0.
  java::lang::System::out->println(s);
}

==> sampSTL.cc <==
#include <stream.h>

// Note that this function can not call any Java methods
// that can throw exceptions, nor can it include cni.h.

void callSTLcode()
{
  cout << "Hello, C++" << endl;
}

==> sample.java <==
public class sample {
  public native void myNative(String s);

  public void myJava(String s)
  {
    s = s + ", Java";
    System.out.println(s);
  }

  public static void main(String args[]) {
    sample x = new sample();
    x.myJava("Hello");
    x.myNative("Hello, Java (from C++)");
    x.myJava("Goodbye");
  }
}