Software Access Modifiers

Question 1

What are Software Access Modifiers (SAMs)

Answer 1

• They are keywords in object oriented languages: C++, Java, Python etc.
• These set the accessibility of classes, methods and other members

Question 2

What are the 3 access modifiers

Answer 2

• Public
• Protected
• Private

Question 3

Level Access Modifiers

Answer 3

Top Level - can use public
Member Level - can use public, private and protected

Question 4

Top Level

Answer 4

• Declared with public access modifiers: Visible to all classes everywhere
• Declared with no access modifier: Visible only to classes within its own package

Question 5

Member level

Answer 5

no access and public same as Top level

-Class member declared with private access modifier: can only
be accessed by its own class
-
Class member declared with protected access modifier: can only be accessed by classes in its own package and subclasses in another package

Question 6

Class

Answer 6

Always has access to its own members

Question 7

Package

Answer 7

Can only access public, protected and package-private (no modifier) members

Question 8

Subclass

Answer 8

can only access public and protected members

Question 9

World

Answer 9

can only access public members

Question 10

How do Access levels affect programming

Answer 10

1. Classes coming from another source- the access levels determine which members of those classes your own classes can use
2. When writing a class - you need to decide what access level every member variable and every method in your class should have

Question 11

Why use access modifiers

Answer 11

Security viewpoint - encapsulation stops class members from being changed in an uncontrollable way
Programming viewpoint - changes made to a public class variable could mean changing the code everywhere that uses that variable

Question 12

Choosing Access Modifiers

Answer 12

• Use the most restrictive access level that makes sense for a particular class member
• Use private unless you have a good reason not too
• Avoid public fields except for constants which cannot be changed

Question 13

Immutable objects

Answer 13

• It is an object whose internal state remains constant after it has been created.