Methods & Classes II

Question 1

What are advantages of using classes?

Answer 1

Links Data with code manipulation

Controls access

Question 2

Three Access Modifiers & Default Access

Answer 2

Public
Protected - only applicable to inheritance
Private - accessible only by members of its class

Default access is public

Question 3

What standard methods control access to members?

Answer 3

Get()

Put()

Question 4

Can you pass objects to methods?

Answer 4

Yes, it’s common

Question 5

Call by value

Answer 5

Copies the value of an argument into a parameter

Primitive are passed by value

Question 6

Call by Reference

Answer 6

The reference to an argument is passed to the parameter.

Objects are passed by reference

Question 7

Will changes to an object inside a method affect the original object?

Answer 7

Yes

Question 8

Method Overloading

Answer 8

When two or more methods within the same class share the same name with different parameters.

E.g. Constructors

Question 9

How is the correct method chosen if it is overloaded?

Answer 9

By matching arguments with parameters.

Question 10

Recursion

Answer 10

A method calling itself

E.g. A factorial

Question 11

What happens during recursion?

Answer 11

New local variables & parameters are allocated storage on the stack & the method is executed with these new variables.

Question 12

Does a recursive call make a new copy of the method?

Answer 12

No, just the arguments are new.

Question 13

What happens when there are too many recursive calls to a method?

Answer 13

A stack overrun

Question 14

Why do recursion rather than iteration?

Answer 14

Some types of algorithms can be more clear & simple

Question 15

How do you end the loop of recursive calls within a method?

Answer 15

You must include a conditional statement to force the method to return without recursion.

Question 16

When can you access a class member without referencing an object?

Answer 16

If that member is declared static.

You don’t need to create an object prior to accessing a static member.

Ex: className.member

Static variables are essentially global variables

Question 17

Which can be static - methods or variables?

Answer 17

Both

Question 18

What restrictions do static methods have?

Answer 18

They can
directly call only other static methods
access only static data
do not have a this reference

Question 19

When is a static block executed?

Answer 19

When a class is first loaded, before it is used for anything else & before objects are constructed.

Question 20

Can classes be nested?

Answer 20

Yes - a nested class is declared within another class.

Question 21

What are inner classes?

What can they access?

Answer 21

Non-static nested classes

They can access all variables & methods of the outer class.

Question 22

What are the advantages of nesting a class?

Answer 22

It creates a localized class that is not known outside its block

Question 23

Varargs method

Answer 23

A method that takes a variable number of arguments depending on its precise usage.

Question 24

Varargs method syntax

Answer 24

int …v

Specified by ellipses …

The arguments are stored in an array referenced by the name given.

Question 25

Can you combine normal & variable parameters?

Answer 25

Yes, but the varargs must be the last declared & there can only be one.

Question 26

Ambiguity errors

Answer 26

Can occur due to varargs & overloading. Often exposes conceptual flaws in the code.