2 - Data Types, Statements, And Expressions in Java FS 2014-2015

8/9/2019 2 - Data Types, Statements, And Expressions in Java FS 2014-2015

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DATA TYPES, STATEMENTS,

AND EXPRESSIONS IN JAVAfundamentals of object-oriented programming


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BASIC SYNTAX

CASE SENSITIVITY

CLASS NAME

PROGRAM FILE NAME METHOD NAMES

public static void main(String[] args)


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BASIC SYNTAX

DEALING WITHKEYWORDS

a word that has a special meaning defined by the Java

programming language


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BASIC SYNTAX

STATEMENTS

simply create variables that you can use to store data

DECLARATION STATEMENT

performs calculations change values of variables, call

methods, and create objects

EXPRESSION STATEMENT

determine the order that statements are executed

CONTROL FLOW STATEMENT


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BASIC SYNTAX

WHITE SPACErefers to one or more consecutive space characters, tab

characters, or line breaks

COMMENTSa bit of text that provides explanations of your code

completely ignored by the compiler

END-OF-LINE COMMENT begins with the sequence // and ends at the end of the line

TRADITIONAL COMMENT begins with the sequence /* and ends with the sequence */ and can span

multiple lines


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BASIC SYNTAX

IDENTIFIERSa word that you make up to a Java programming

element by name

ALL IDENTIFIERS SHOULD BEGIN WITH a letter

currency character

underscore

AFTER THE FIRST CHARACTER, IDENTIFIERS CANHAVE ANY COMBINATION OF CHARACTERS

A KEYWORD CANNOT BE USED AS AN IDENTIFIER


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BASIC SYNTAX

CREATING AN OBJECTFROM A CLASS

className variableName = new ClassName();

NEW KEYWORD

used to create instances / new objects

THREE STEPS CREATING AN INSTANCE FROM A CLASS declaration

instantiation

initialization


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VARIABLES

a variable thats declared within the body of a method

LOCAL VARIABLE

BASIC FORM OF A VARIABLE DECLARATION type identifier;

TYPES OF VARIABLES

a variable that any method in a class can access

CLASS VARIABLE

associated with the instances of classes

INSTANCE VARIABLE


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BASIC DATA TYPES

TWO DATA TYPES INJAVA

predefined by the Java language and named by a keyword

PRIMITIVE DATA TYPE

reference variables are created using defined constructors

of the classes

REFERENCE / OBJECT DATA TYPE


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INTEGER TYPES

BYTE DATA TYPE an 8-bit signed twos complement integer

-128 to 127

SHORT DATA TYPE

a 16-bit signed twos complement integer -32,768 to 32,767

INT DATA TYPE a 32-bit signed twos complement integer

-2,147,4838,648 to 2, 147,483,647

LONG DATA TYPE a 64-bit signed twos complement integer

-9,223,372,036,854,775,808 to 9,223,372,036,854,775,808


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FLOATING TYPE

FLOAT DATA TYPE a single-precision 32-bit IEEE 754 floating point

precision is only about 6 or 7 decimal digits

DOUBLE DATA TYPE

a double-precision 64-bit IEEE 754 floating point precision is about 15 decimal digits

EXPONENTIAL NOTATION

used by floating point numbers to store their values records two

numbers: a base value (mantissa), and an exponent


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WRAPPER CLASSES

wraps a primitive value to behave like an object used to convert

primitive values to strings and vice versa

Primitive Type Wrapper Class

int Integer

short Short

long Long

byte Byte

float Float

double Double

char Character

boolean Boolean


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STRING PRIMITIVES TO STRINGS

Java automatically converts primitive values to string values

explicit conversion from primitives to a string use toString() method of the

primitive types wrapper class

STRINGS TO PRIMITIVES

converting a string to a primitive type uses aparse method of theappropriate wrapper class

Wrapper Class Wrapper Class

Integer parseInt(String)

Short parseShort(String)

Long parseLong(String)

Byte parseByte(String)

Float parseFloat(String)

Double parseDouble(String)

Character {none}

Boolean parseBoolean(String)


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LITERAL

a source code representation of a fixed value

INTEGER TYPES

byte can be expressed in decimal, hexadecimal, or octal number systems

CHARACTER AND STRING LITERALS character literals are specified by enclosing the character on a pair of apostrophe ()

String literals enclose a sequence of characters between a pair of quotation marks()

ESCAPE SEQUENCES let you create literals for characters (e.g. , , space, tab, newline, etc) that cant

otherwise be typed within a character or String literal


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MODIFIERS

keywords that you add to those definitions to change their meaning

TYPES OF MODIFIERS

ACCESS MODIFIERS set access levels for classes, variables, methods, and constructors

access levels are: default,private,public, andprotected

NON-ACCESS MODIFIERS used to achieve many other functionality

static,final, abstract, synchronized, andvolatile


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OPERATORS

a special symbol or keyword used to designate a mathematical or some other type ofoperation that can be performed on one or more values, called operands

ARITHMETIC OPERATORS (+ - * / % ++ --)

BASIC OPERATORS

RELATIONAL OPERATORS (== != > < >=


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OPERATORS

PRECEDENCE OF OPERATORSCategory Operator Associativity

Postfix () [] . (dot operator) Left to right

Unary ++ -- ! ~ Right to left

Multiplicative * / % Left to right

Additive + - Left to right

Relational > >= <


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CASTING

a way to convert a variable from one data type to another data type

TWO TYPES OF CASTING PRIMITIVE DATA TYPE CASTING

implicit casting assigned to a data type of higher size (widening conversion)

explicit casting a data type of higher size cannot be assigned to a data type of

lower size (narrowing conversion)

REFERENCE TYPE CASTING


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SELECTION CONTROLIF STATEMENT

lets you execute a single statement or a block of statements only if

a boolean expression evaluates to true

General form: if(boolean expression)

statement

IF-ELSE STATEMENT

adds an additional element to a basic if statement: a statement or

block thats executed if the boolean expression is not true

General form: if(boolean expression)

statement

else

statement


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SELECTION CONTROL

ELSE IF STATEMENTa common pattern for nested if statements statement in

the else part happens to be another if statement

General form: if(boolean expression 1)

statement 1

else if(boolean expression 2)

satement 2

else if(boolean expression 3)

satement 3


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SELECTION CONTROL

SWITCH STATEMENTallows a variable to be tested for equality against a list of

values each value is a case

General form: switch (boolean expression) {

case value1:statement

break;

case value2:statement

default:

}


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ITERATION CONTROL

WHILE LOOPa type of loop that executes continuously as long as some

conditional expression evaluates to true

General form: while (boolean expression)

statement

DO LOOP

similar to a while loop, but with a critical difference: a do

loop is guaranteed to execute at least once

General form: do {

statement

}while (boolean expression);


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ITERATION CONTROL

FOR LOOPmaintains a counter variable that is, a variable whose

value is increased time the body of the loop is executed

General form: for(initialization expression; test expression; count expression)statement

BREAK KEYWORD used to stop the entire loop

stop the execution of innermost and execute next line of code after the block

CONTINUE KEYWORD causes the loop to immediately jump to the next iteration of the loop


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ARRAY

a data structure which stores a fixed-size sequential

collection of elements of the same type

DECLARING ARRAY VARIABLESdataType[]arrayReferenceVariable ordataType arrayReferenceVariable[]

CREATING ARRAYSarrayReferenceVariable =new dataType[arraySize];

dataType[]arrayReferenceVariable = {value0,value1,value2, ,valuen};

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2 - Data Types, Statements, And Expressions in Java FS 2014-2015