Calling non-public methods

A very small and simple hack to call non-public methods in Java.

Problem
~~~~~~~
A non-public method of a class has to be called from another class. Both the classes are in different packages.

package apipackage;
public class APIClass {
 void methodA() {
   System.out.println("methodA Called");
 }
}

package clientpackage;
public class ClientClass {
 void methodACaller() {
 ...
 ...
 ...
 }
}

Fill in the dotted lines to call methodA of APIClass.

Solution
~~~~~~~~

package clientpackage;
// import statements
public class ClientClass {
 void methodACaller() {
  apipackage.APIClass apiObject = new apipackage.APIClass();
  Method methodA = apipackage.APIClass.class.getDeclaredMethod("methodA", null);
  methodA.setAccessible(true); // this makes it possible to invoke methodA
  methodA.invoke(apiObject, null);
 }
}

One important thing to remember is to call "getDeclaredMethod" and not "getMethod" to obtain the Method object.

From Java docs:
"getMethod returns a Method object that reflects the specified public member method of the class"

/*
   This would not work
   Method methodA = apipackage.APIClass.class.getMethod("methodA", null);
*/