Comp 1409 Pre-Midterm Flashcards
What is a Java Class and an example?
A file that describes a general category in terms of data and behaviours ie a book class describes title, author, date written, that the book can be opened and closed etc
What is an object?
One specific instance of a class eg in a book class the object would be the title. Every book will have a title.
What are instance variables?
an individual piece of data within a class
nouns or adjectives should be used to describe what kind of data?
Instance variables
What are the 4 primitive data types?
int, double , boolean and char
What are the reference (or object) data types?
String and classes
What are 2 visibility modifiers (access modifiers) from lesson 2?
public or private, accessible from any class or only from within a class
instance variables should always be be private?
True
What is a constructor and and what does it do?
A constructor is a special method used to initialize objects when an object of a class is created (is called automatically). Is used to set sensible initial values for object attributes.
Constructors should be marked public
F
Constructors should have Javadoc comments
T with @param tags explainging each parameter’s conditions
What’s the difference between formal arguments and actual arguments
Formal arguments are instance variables in a constructor where as an actual argument is the data in the argument. IE formal argument is variable “title” where as the the actual argument would be “Star Wars”
What is a method?
An instruction, a function, a verb
How should methods be named?
As verbs
What must methods always have to compile?
a return type even if its void
Do accessors need the variable return type or should it be void?
It should be the same return type as the instance variable that is getting returned
Do you think there are usually more getters than setters?
I hope so because thats what big boss says
Are mutators returning the same variable type as the instance variables they are changing?
No they return void
What are local variables?
defined within a method. Are created when the method called and destroyed when it ends.
- locals scope only
- private visibility modifier/no visibility modifier
Where are instance variables?
Defined within a class. Are created when an object is created and destroyed when the object is destroyed
What are static variables?
Belong to the class not each object
- Each object uses the single instance of the instance of the variable
- Declared with keyword static - public static int population
- no object required
What are static methods
belong to a class can only use class (static) variables not instance variables Can be called without object instantiation declared with a static keyword
What is the final variables?
Instance variables that accept data once and never change
Keyword final
Constants - what is they?
Data that are only set once Declared with static final keywords at class level used to represent things that dont change (sucha s the value of Pi) Often called symbolic constants, named with all caps
Are a static method and static variable acceptable?
Yeeess
Are instance method and instance variable acceptable?
yes
Are instance methods and static variables acceptable?
Oh sure, bud
Are Static Methods and Instance variables acceptable?
Not okay. Not okay at all.
If variable is: Accessible only to the method it is declared in no access modifier no default values It must be what kind of variable?
Local
Variable is Accessible all throughout the class private declared within the class li
instance
Which operations then assign shoulod you not do? (operation than issign be x += number
dont do *=, /=, %=
What are the three ways an overloaded constructor can work/be differentiated?
- ifferent number of parameters
- different type of parameters
- different order of parameters
Whats the formatt for switch/case statements?
ublic void printGradeRange(char letterGrade){switch(letterGrade){case(‘A’):case(‘a’):System.out.println(“80 to 100”);break;case(‘B’):case(‘b’):System.out.println(“60 to 79”)
default:
get rekt
