Section 1
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Object is the _____________ of every Java object
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Last updated
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Date created
Mar 14, 2020
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Section 1
(50 cards)
Object is the _____________ of every Java object
superclass
double
Bit depth: 64 Default value: 0.0 Wrapper class: Double signed floating-point
Pillars of OOP
Encapsulation, Inheritance, Polymorphism, Abstraction
Where do primitive types live?
Live on the stack
JVM
Java Virtual Machine - translates compiled java code into instructions your operating system can understand
What does static mean?
Belongs to the class, NOT any particular instance of the class
autoboxing
the automatic conversion of a primitive datatype into its wrapper class
Behavior
functions belonging to the object/method
JDK
Java Development Kit - the kit for developing in java, JRE, and compiler
What is the "extends" keyword used for?
Used to describe the direct subclass of a superclass. ex: vehicle extends machine
reference-type
any object of the declared type
JRE
Java Runtime Environment - includes the JVM and the libraries needed to run java programs
what is the heap for?
Dynamic memory allocation
Where do reference variables live?
Live on the heap
What does it mean to instantiate?
To instantiate is to create an object
Package
Namespace - organizes code into logical groups
Protected access modifier
Only accessible via inheritance (methods and variables only) or within same package
Char
Bit depth: 16 (unicode) Default value: null character Wrapper class: Character
When accessing info in java, where is it stored?
in the stack and the heap
What do .java source files get compiled into?
.class file
autounboxing
the automatic conversion of a wrapper class into a primitive datatype
An object is a(n) ________________ of a class
instance
Encapsulation
Concealing the internal state of an object -> requires interaction with internal state to occur only through methods (private instance variables with setter and getter methods)
float
Bit depth: 32 Default value: 0.0 Wrapper class: Float signed floating-point
Abstraction
-Concealing implementation details and exposing only the necessary functionality -What the object does, not how it does it
State
The properties/fields
short
Bit depthL 16 Default value: 0 Wrapper class: Short signed integer
widening
Converting to a larger numeric type
long
Bit depth: 64 Default value: 0 Wrapper class: Long signed integer
Polymorphism
Referring to a program element in multiple ways
int
Bit depth: 32 Default value: 0 Wrapper class: Integer signed integer
What is a class?
A blueprint/template
narrowing
converting to a smaller numeric type
Differences between a .java and a .class file
-A .java file is what we write and can read, a .class file is read by the machine -A .java file is our source code -A .class file is made by javac, which compiles it -.java runs the program
What is the stack used for?
local variables and method calls
What does it mean that java is object-oriented?
Our unit of programmability is the object
How many direct supertypes can every type have?
One
___________ is within ____________ which is within _____________
JVM is within JRE which is within JDK
What does it mean that java is strongly-typed?
Must declare variable with datatypes, can't change datatype
boolean
Bit depth: varies Default value: false Wrapper class: Boolean
Polymorphism for datatypes
A class can be treated as any of its supertypes (multiple "is-a" relationships)
Access modifiers
How we control access to program elements
What is a primitive datatype?
Just a value
byte
Bit depth: 8 Default value: 0 Wrapper class: Byte signed integer
Public access modifier
Any class and any package can access (fine for classes, methods, and variables)
What is an object?
A software entity with states and behavior
Private access modifier
Only within same class
Polymorphism for methods
-Can be overwritten in subclasses -Can be overloaded in the subclasses
Inheritance
Sharing of common states and behaviors between subclasses and superclasses
Default access modifier
Within same package
Section 2
(4 cards)