Scjp

Summary

Questions for the Java Programmer Cert, Section 1 (Declarations, Initialization and Scoping).

Exam Objectives - Section 1

Basics

Term (memorize)	Description (memorize)
Class	Blueprint used to make an object
Object	main building-block of java applications
Method	Java word for function
Member variables	variables defined in a class
2 main things in a class	methods and member variables
Usually required to call a method?	an object

Basic Code

Question (memorize)	Answer (memorize)
Define a class	class MyClass { // Members // Methods }
Define a method	void myMethod() { // Body }
Define a member	int i;
Define a main() method	public static void main( String[] args ) { // Body }
Create an object	MyClass myObject = new MyClass();
Call a method	myObject.myMethod();

Object-Oriented concepts

Java is a thoroughly object-oriented language. Objects are the primary building blocks of Java applications. You can think of objects as containers for variables and methods (functions). When speaking at a high level, "object" and "class" are sometimes used interchangably, even though a class is a definition used to create an object.

 

Question (memorize)	Answer (memorize)
OO	Object-Oriented
Subclass	A child class of another class
Example of superclass and subclass	Employee, Engineer
Method overriding	Method in a subclass with same signature as superclass
Method overloading	Method in a class with same name as another method
Keyword for subclassing	MySuperclass extends MySubclass
What does a subclass inherit from superclass?	methods (non-private) and member variables

Synonyms

Synonyms are rampant in the Java world. For example, it isn't uncommon for someone to use "object" and "instance" in the same sentence to refer to the same thing. This can be confusing to newbies.

 

Term (memorize)	Synonym (memorize)
Superclass	Parent class, Base class
Subclass	Child class, Derived class
Function	Method
Instance	Object
Type	Class
Member	Member Variable

Classes

Question (memorize)	Answer (memorize)
Abstract class	Class that can't be instantiated
What is a top-level class?	A class not defined within another class
Modifiers allowed for a top-level class?	public, abstract, final
Final class	A class that can't be subclassed

Methods

Question (memorize)	Answer (memorize)
Static method	Can be called without an object
Abstract method	Method with no body
Name all access modifiers	public private default (package) protected
Final method	A method that can't be overridden

Types

Question (memorize)	Answer (memorize)
All integer types are...	signed
In Java, variables are either...	- references to objects - or, primitive types
Name all primitive types	- boolean, char - byte, short, int, long - float double

 

Primitive (memorize)	Description (memorize)
boolean	1 bit (true or false)
char	2 byte unicode character (0 to 216-1)
byte	1 byte integer (-27 to 27-1)
short	2 byte integer (-215 to 215-1)
int	4 byte integer (-231 to 231-1)
long	8 byte integer (-263 to 263-1)
float	4 byte floating point
double	8 byte floating point

Character Escape Codes

Escape Code (memorize)	Description (memorize)
\n	New line
\t	Tab
\b	Backspace
\r	Carriage return
\f	Formfeed
\\	Backslash
\'	Single quotation mark
\"	Double quotation mark
\d	Octal
\xd	Hexadecimal
\ud	Unicode character

Gotcha's

Question (memorize)	Answer (memorize)
Can a class be static?	Yes, but only an inner class
Can a non-abstract class have an abstract method?	no
Can an abstract class have a non-abstract method?	yes

Advanced

Question (memorize)	Answer (memorize)
Name all modifiers	access: private, default (package), protected, public non-access: static abstract final synchronized native strictfp transient volatile