Final answer:
If the main() method of a "testing" class tries to access a private instance variable of an object using dot notation, it will result in a compiler error. To access a private instance variable from outside the class, you can use getter and setter methods.
Step-by-step explanation:
If the main() method of a "testing" class tries to access a private instance variable of an object using dot notation, it will result in a compiler error. Private instance variables are only accessible inside the class where they are declared. Dot notation is used to access instance variables of an object from outside the class. Since the main() method is not part of the class that declares the private instance variable, it does not have access to it.
To access a private instance variable from outside the class, you can use getter and setter methods. Getter methods allow you to retrieve the value of the private instance variable, while setter methods allow you to set a new value for the variable. This ensures that the variable remains private and can only be accessed and modified through the designated methods.