Sorry, as it's pretty much the only JNI tutorial
in existence I'd assumed it would be well known:

Sample1.java:

public class Sample1
{
  public native int intMethod(int n);
  public native boolean booleanMethod(boolean bool);
  public native String stringMethod(String text);
  public native int intArrayMethod(int[] intArray);

  public static void main(String[] args)
  {
    System.loadLibrary("Sample1");
    Sample1 sample = new Sample1();
    int     square = sample.intMethod(5);
    boolean bool   = sample.booleanMethod(true);
    String  text   = sample.stringMethod("JAVA");
    int     sum    = sample.intArrayMethod(
                        new int[]{1,1,2,3,5,8,13} );

    System.out.println("intMethod: " + square);
    System.out.println("booleanMethod: " + bool);
    System.out.println("stringMethod: " + text);
    System.out.println("intArrayMethod: " + sum);
  }
}

Sample1.c:

#include "Sample1.h"
#include <string.h>

JNIEXPORT jint JNICALL Java_Sample1_intMethod
  (JNIEnv *env, jobject obj, jint num) {
   return num * num;
}

JNIEXPORT jboolean JNICALL Java_Sample1_booleanMethod
  (JNIEnv *env, jobject obj, jboolean boolean) {
  return !boolean;
}

JNIEXPORT jstring JNICALL Java_Sample1_stringMethod
  (JNIEnv *env, jobject obj, jstring string) {
    const char *str = (*env)->GetStringUTFChars(env, string, 0);
    char cap[128];
    strcpy(cap, str);
    (*env)->ReleaseStringUTFChars(env, string, str);
    return (*env)->NewStringUTF(env, strupr(cap));
}

JNIEXPORT jint JNICALL Java_Sample1_intArrayMethod
  (JNIEnv *env, jobject obj, jintArray array) {
    int i, sum = 0;
    jsize len = (*env)->GetArrayLength(env, array);
    jint *body = (*env)->GetIntArrayElements(env, array, 0);
    for (i=0; i<len; i++)
    {    sum += body[i];
    }
    (*env)->ReleaseIntArrayElements(env, array, body, 0);
    return sum;
}

Sample1.h created by running javah on Sample1.java.
Though it occurs to me that I did this on the Windows
machine and copied the result to the Linux system;
is this a possible cause?  The problem is occuring
in the summation in Java_Sample1_intArrayMethod.