jsizes.c

// gcc -I$JAVA_HOME/include -I$JAVA_HOME/include/linux jsizes.c -o jsizes && ./jsizes

#include <stdio.h>
#include <jni.h>

int main() {
  printf("jboolean %li\n", sizeof (jboolean));
  printf("jbyte %li\n", sizeof (jbyte));
  printf("jchar %li\n", sizeof (jchar));
  printf("jshort %li\n", sizeof (jshort));
  printf("jint %li\n", sizeof (jint));
  printf("jlong %li\n", sizeof (jlong));
  printf("jfloat %li\n", sizeof (jfloat));
  printf("jdouble %li\n", sizeof (jdouble));
  printf("jsize %li\n", sizeof (jsize));
  printf("\n");

  printf("unsigned char %li\n", sizeof(unsigned char));
  printf("unsigned short %li\n", sizeof(unsigned short));
  printf("unsigned int %li\n", sizeof(unsigned int));
  printf("unsigned long %li\n", sizeof(unsigned long));
  printf("unsigned long long %li\n", sizeof(unsigned long long));

  return 0;
}

sizes.c

#include <stdio.h>

int main() {
  printf("int %li\n", sizeof (int));
  printf("long %li\n", sizeof (long));
  printf("size_t %li\n", sizeof (size_t));
  return 0;
}