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Is it permitted in Java to have a an abstract method within a class and then have it's implementation in an other with a native language using JNI.
example:
abstract class Mommy {
abstract protected void call();
}
class Son extends Mommy {
native protected void call() /*
'native code'
*/
}
What is the expected behaviour is it a runtime error that may occurs or everything is fine with "workaround" ?
747
An abstract method doesn't have any implementation (method body). A class containing abstract methods should also be abstract. We cannot create objects of an abstract class. To implement features of an abstract class, we inherit subclasses from it and create objects of the subclass.
Native methods are implemented mostly in C and compiled to native code which runs directly on the machine. This is in contrast to normal methods, which are implemented in Java and compiled to Java byte code, which is executed by the Java Virtual Machine (JVM).
If you want to have default implementation of a method in your abstract class, you have to use non-abstract methods. In abstract classes, you can declare fields with or without static and final modifiers. And concrete methods can be not just public, but also default, protected or private.
Abstract class in Java is similar to interface except that it can contain default method implementation. An abstract class can have an abstract method without body and it can have methods with implementation also. abstract keyword is used to create a abstract class and method.
What is the expected behaviour is it a runtime error that may occurs or everything is fine with "workaround" ?
Provided that you implement the native method (correctly) and load the native library containing the implementation, then everything works.
I wonder if bug prone or against any good/best practices?
Nope, and nope.
Or at least, it is not more bug prone or more against "best practice" than any use of native code.
By the way, you really ought to read James Bach's "No Best Practices" article before you bandy around dodgy terms like "best practice".
93
Seems to be working just fine. This is quite cool solution in case you want to easily switch between native implementations.
https://github.com/mkowsiak/jnicookbook/tree/master/recipes/recipeNo030
and description inside JNI Cookbook can give you quick overview on the solution
http://jnicookbook.owsiak.org/recipe-no-030/
35
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