associating jobject with a value

Question

jclass object = (*env)->FindClass(env,"java/lang/Integer") // C Code

Is there any way i can associate an integer value with object ? I want object to contain/point to an integer number.

Answer 1

Make sure you read an understand Confusing jclass with jobject in the Pitfalls section of the JNI guide.

FindClass(env, "Foo") returns (a handle to) an object of type java.lang.Class . It is conceptually equivalent to the Class.forName(String) static method: it does not return an instance of the class you give it as a parameter ( Foo ). It returns an object of type Class which represents that class.

What you can do with a jclass (or a Class ) is find the constructor you want , and invoke that constructor to create an object of type Foo .

The JNI guide has an example of how you do this in the Invoking constructors for class String . Doing it for class Integer is similar, except for the method signature.

You'd do something like:

jclass clazz = (*env)->FindClass(env, "java/lang/Integer");
jmethodID mid = (*env)->GetMethodID(env, clazz, "<init>", "(I)V");
jobject mint = (*env)->NewObject(env, clazz, mid, 42); // your desired value here

(Requires error checking.)