About Question enthuware.ocajp.i.v7.2.1403 :

[ftejada]

To access's Donkey's location instance variable, cast your reference to Donkey first. Like so:
((Donkey)m).location

Since Donkey's location field has default access modifier, ((Donkey)m).location from TestClass will generate a compile-time error. To fix this we can:

• Change Donkey's location access modifier to public

• Use reflection:

Code: Select all

// in file TestClass.java
package px;
import p1.Movable;
import p2.Donkey;
import java.lang.reflect.Field;

public class TestClass {
    public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException {
        Movable m = new Donkey();
        m.move(10);
        m.moveBack(20);
	Field donkeyLocation = m.getClass().getDeclaredField("location"); // retrieves Donkey's location field
	donkeyLocation.setAccessible(true); // suppresses Java access control to make it readable
	System.out.println(donkeyLocation.get(m)); //prints 190
    }
}

• Move TestClass.java file to package p2 or Donkey.java file to package px

[admin]

Correct. Reflection is not on the ocp exam, so you can leave that though.

[baichen7788]

why it prints interface location=0 instead of location in object?