added a test class for the Java API plus a small refinement in the implementation for the binding

src/runtime/java/Test.java

@@ -0,0 +1,8 @@
+import org.grammaticalframework.*;
+
+public class Test {
+	public static void main(String[] args) {
+		PGF gr = PGF.readPGF("/home/krasimir/www.grammaticalframework.org/treebanks/PennTreebank/ParseEngAbs.pgf");
+		gr.close();
+	}
+}

src/runtime/java/jpgf.c

@@ -4,17 +4,20 @@
 
 JNIEXPORT jobject JNICALL 
 Java_org_grammaticalframework_PGF_readPGF(JNIEnv *env, jclass cls, jstring s)
-{
-	const char *fpath = (*env)->GetStringUTFChars(env, s, 0); 
- 
+{ 
 	GuPool* pool = gu_new_pool();
 	GuPool* tmp_pool = gu_local_pool();
 
 	// Create an exception frame that catches all errors.
 	GuExn* err = gu_new_exn(NULL, gu_kind(type), tmp_pool);
 
+	const char *fpath = (*env)->GetStringUTFChars(env, s, 0); 
+
 	// Read the PGF grammar.
 	PgfPGF* pgf = pgf_read(fpath, pool, err);
+
+	(*env)->ReleaseStringUTFChars(env, s, fpath);
+
 	if (!gu_ok(err)) {
 		gu_pool_free(pool);
 		gu_pool_free(tmp_pool);
@@ -23,9 +26,13 @@ Java_org_grammaticalframework_PGF_readPGF(JNIEnv *env, jclass cls, jstring s)
 
 	gu_pool_free(tmp_pool);
 
-	(*env)->ReleaseStringUTFChars(env, s, fpath);
+	jmethodID constrId = (*env)->GetMethodID(env, cls, "<init>", "(JJ)V");
 
-	jmethodID constrId = (*env)->GetMethodID(env, cls, "<init>", "(II)V");
-
-	return (*env)->NewObject(env, cls, constrId, (int) pool, (int) pgf);
+	return (*env)->NewObject(env, cls, constrId, (long) pool, (long) pgf);
+}
+
+JNIEXPORT void JNICALL 
+Java_org_grammaticalframework_PGF_free(JNIEnv* env, jclass cls, jlong pool)
+{
+	gu_pool_free((GuPool*) pool);
 }

src/runtime/java/org/grammaticalframework/PGF.java

@@ -1,25 +1,31 @@
 package org.grammaticalframework;
 
 public class PGF {
-	static native PGF readPGF(String path); 
-
-	private int pool;
-	private int gr;
+	public  static native PGF readPGF(String path); 
 	
-	private PGF(int pool, int gr) {
+	public void close() {
+		if (pool != 0) {
+			free(pool);
+			pool = 0;
+			gr = 0;
+		}
+	}
+
+	private static native void free(long pool);
+
+	private long pool;
+	private long gr;
+	
+	private PGF(long pool, long gr) {
 		this.pool = pool;
 		this.gr   = gr;
 	}
 	
+	protected void finalize () throws Throwable {
+		close();
+	}
+	
 	static { 
          System.loadLibrary("jpgf");
     }
-    
-    public void test() {
-		System.out.println("pool="+pool+", gr="+gr);
-	}
-	
-    public static void main(String[] args) {
-		readPGF("/home/krasimir/www.grammaticalframework.org/treebanks/PennTreebank/ParseEngAbs.pgf").test();
-	}
 }