Three permissible styles of comments line comments e.g. //comments on a line by themselves block...
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Transcript of Three permissible styles of comments line comments e.g. //comments on a line by themselves block...
Three permissible styles of comments line comments
e.g. //comments on a line by themselves block comments
e.g. /*comments on one line or can be extended across as many lines as needed */
Javadoc comments e.g./**javadoc comments generate
documentation with a program named javadoc*/
The java source code has to be saved with an extension .java
The filename and the classname must be the same
Case sensitive
Requirements when defining a classname: A classname must begin with a letter of
the alphabet, an underscore or a dollar sign.
A classname can contain only letter, digits, underscore or dollar signs.
A classname cannot be a Java programming language reserved keyword
Classname should be nouns in mixed case. Variable names declared usually begin
with a lowercase first letter and should be in mixed case
Constant variables declared usually are all uppercase with the words separated by underscore.
Method name(procedures) declared should be verbs in mixed case with the first letter in lower case.
Whitespace used to organize your program code to make reading easier.
The code between a pair of curly brackets ‘{‘ and ‘}’ within any class or method is known as a block.
All statements in Java programming ends with a semicolon( ; ).
A statement is a single line of code.
names that are given to a variable, class or a method
case sensitiveRequirements in declaring an identifier:
can used letters, digits, dollar signs and underscores
must begin with a letter, an underscore or a dollar sign
no maximum length of characters must not use of reserved words
Identifiers Valid Examples Invalid Examples
e.g. student name
studentName, student_name
student Name,Student-name
e.g. class code classCode,class_code
#code, class
e.g. fee payment
$payment,payFee
Pay Fee, pay-fee
The basic building blocks of the language
abstract do implement private throw
boolean double import protected throws
break else instanceOf public transient
byte extends int return true
case false interface short try
catch final long static void
char finally native super volatile
class float new switch white
continue for null synchronized this
default if package
Two types of identifiers in JAVA Programming:
Constants- data or values stored that do not change during the execution of the program
Variables- data or values stored that can be changed during the execution of the program
static final type identifier=value;
The type in the declaration refers to the data type(which will be seen later in this chapter).
The identifier refers to the name of the constant being defined.
Type ExamplesShortLongInt
234226357284L13324
Char String
‘a’“Hello World”
Boolean True or false
A data type that identifies the type of data that the variable will store
An identifier that is the variable’s name
An optional assigned value, if we want a variable to contain an initial value
A semicolon to end the declaration
type identifier;The type refers to the data type, and
identifier is the name of the variable being defined.
type identifier1, identifier2;To define more than one variable with the
same data type, the names will be separated by a comma.
We can assign a value to a variable at the time of declaration or at any point later on after the variable is being declared.syntax:
type identifier=value;or
type identifier;identifier=value;
Primitive boolean byte char double float int long short
Reference array class
Logical Boolean – can hold only true or false
e.g. boolean answer=true;
IntegerType Minimum Range Maximum Range Size
Byte -128 127 8 bits
Short -32,768 32,767 16 bits
Int -2,147,483,648 2,147,483,648 32bits
Long -9,223,372.036,854,775,808
9,223,372.036,854,775,808
64 bits
Floating Point
Character char
e.g. char num = ‘8’;
Type Minimum Range
Maximum Range
Size
Float -1.7e-308 1.7e+308 32bits
Double 3.4e-038 3.4+038 64 bits
Array A list of variables which all have the
same data types and same nameSyntax:
type array_name[];or
type [] array_name;
Class String
Variable name refers to the location in memory rather than to a particular value.
e.g. String myWord=“Java is my favorite subject”;
Used to define the shape and function of Java code
Separator Function
{ } To separate blocks of code
; To delimit the end of a line of code
, To separate a list of values or variables
[ ] To define and reference arrays
( ) To indicate precedence in an expression
. To separate a class from a subclass
Symbols used with data or variables to create mathematical or logical expressions Types:
Arithmetic operator Relational or comparison operator Logical operator Assignment operator Increment/decrement operator
Arithmetic operator
Operator Description
+ Addition
- Subtraction
* Multiplication
/ Division
% Modulus
Relational or comparison operator Allows us to compare two items
Operator Description
< Less than
> Greater than
== equal to
<= less than or equal
>= greater than or equal
!= not equal to
Logical operator Used to combine compound conditions
Operator Description
|| OR
&& AND
! NOT
Assignment operator Represented by the equals sign (=)
Initialization- assignment made when we declare a variable
Assignment-assignment made later
Increment or decrement operator
Used to store any characters that includes non-printing characters
Operator Description
\b Backspace
\t Tab
\n New line
\f Form feed
\r Carriage return
\” Double quotation mark
\’ Single quotation mark
\\ backslach