Transcript PPTX

Comments are for people
Header comments supply basic
information about the artifact
Comments also used to describe
class elements
Whitespace is also for people
Blank lines make elements stand out
Indentation is a form of whitespace
Indentation is used to indicate that
what follows is a part of what
proceeded
Indentation is a form of whitespace
Indentation is used to indicate that
what follows is a part of what
proceeded
Keywords are reserved lowercase
words that have special meaning
public – what follows is shareable
class – program or object definition
static – not part of an object
definition
void – method does not return a value
Name of the class
A Java name must be an identifier
Java has syntax rules for stating
what is a valid name; e.g., identifiers
begin with letter and can be followed
letters and numerals
To encourage program understanding
style rules give name understanding
Convention to capitalize the first
letter in a class name
General convention to capitalize
successive words in a name
PrintQuote, main, String, args,
System, out, and println are all names
Convention that identifiers not
indicating a class begin with a lower
case letter
Braces delimit a class definition
Braces delimit a block of code
A program begins executing the code
in method main()
Method main() must be public, static,
and void
Every method has a parameter list
following its name.
The list is contained with a pair of
parentheses.
For some methods, the list is empty
Method main() takes a single
parameter of type String[]
Everybody who is anybody calls that
parameter, args
Following the parameter list is the
body of the method
The method body lists the statements
(i.e., actions) it is to perform when
invoked (started up)
The statements are performed from
top to bottom
The statements are performed from
top to bottom
Because statements are allowed in
general to span multiple lines an
indicator is needed for separating
statements from one another
Java statements are terminated with
a semicolon
The dot is the selection operator
Sometimes multiple selecting is
needed to get a hold of the desired
component
System is the name of a class library
whose elements are automatically
available to a program
The System library has an element
named out
out represents an object configured
to be associated with your display
out has a println() behavior
println() is a method
println() displays text to its display
println() displays the value of its
argument
This use of println() says to print the
literal string ”I’m never going to the
Louvre again.” to its display
A literal string is a sequence of
characters within a pair of the
double-quote characters
This use of println() says to print the
literal string ”-- Joanne Cohoon” to its
display
A program terminates when all of the
statements in method main() are
completed