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Upon completion of this course, the students should be ableto:

1. Describe the features and basic concepts of Java language.

2. Write, compile Java source code and interpret Java byte code usingJava Development Kit (JDK).

3. Implement the key of OOP concepts: classes and objects, inheritanceand polymorphism.

4. Incorporate exception handling in Java Programming.

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Identify identifiers, variables and constants in Javaprogram.Define assignment and expression statements in JavaprogramList numeric data types in Java programImplement numeric data types in Java programExplain character data types in Java program :

Unicode and ASCII codeEscape sequence for special character

Implement character and Boolean data types,operator precedence in Java programs.Define typecasting in Java programsImplement typecasting in Java programs

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Identifiers :The name given to the variables,constants and method.

Rules to naming Identifiers : An identifier must start with a character (A-Z, a-z),an underscore (_) or a dollar sign ($).In an identifier, the letters other than the first one

can be any character except the operators or keywords in Java (Examples: +, -, switch).The special characters such as #, !, @ and ^cannot be used.

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The special characters such as #, !, @ and ^cannot be used.

Blank and tab space cannot be used.

Java is case-sensitive.Keywords listed in Java cannot be used asidentifiers.

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Identifiers Valid/Invalid Reason Quantity Valid Identifier should start with

an alphabet.

1amount Invalid Identifier must not beginwith a number.

$price Valid Identifier can start with a $.my car Invalid Blank spaces not allowed in

an identifier.Total_Price Valid Special symbol underscore

( _ ) can be used in anidentifier.

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Identifiers Valid/Invalid Reason First! Invalid Special character

exclamation mark ( ! )

cannot be used in anidentifier.Number5 Valid Identifier can have

numbers.

Price# Invalid Identifier name must notend with the hash ( # )symbol.

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Identify which of the following are valididentifiers. If it is invalid, explain why.

a. bite the cakeb. troublec. 1stnamed. Bubblee. good-byef. Second!

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Variables :Is the name given to the memory location where avalue is stored.

The name given to the variable is called as identifier.Each variable has :

NameTypeHolds a value that you assign to them

The value can change during programexecution

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Declaration :A Java variable may refer to an object, anarray, or an item of primitive.

Syntax to define a variable : ;

E.g :char grade; // defines a character

int [] grade; // defines a reference to array of intsint age = 25; // defines an integerVector v; // reference to a Vector object

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InitializationsVariables may be initialized as follow :

Primitive type :int i = 3;boolean g = true;

Objects :Button b = null;Employee e = new Employee();

Arrays :int[] a={1,2,3,4};

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Is a value that does not change throughoutprogram execution.Every constant has :

NameTypeValues that are set to them

Variables modified by the static finalkeywords are constant

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Example of a constant value for each datatype is listed as follows:

Integer (Example: 12)Floating-point (Example: 3.1438)Boolean (Example: true/false)Character (Example: a)

String (Example: I go to school)

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Defines the type of the value to be stored in thememory.Data types in Java can be classified into two

groups:Primitive or Built-in data typesReference or User-defined data types

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Java defines eightbasic primitive datatypes.

They are:byteshort

longint

floatdouble

charBoolean

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Primitive Type Description

boolean true/false 1-bit. May take on the valuestrue and false only

byte 8 bits 1 signed bytes (twoscomplement). Covers valuesfrom -128 to 127

char 16 bits(UNICODE)

2 bytes, unsigned, Unicode, 0 to65,535.A char is a single characterwhich can contains a letter, a

digit, a punctuation mark, a tab,a space, or something similar.Char can be implemented by asingle one character enclosed insingle qoute marks such as :

char MyChar =g;

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Primitive Type Description

short 16 bits 2 bytes, signed (twoscomplement), covers value from -32,768 to 32,767

int 32 bits 4 bytes, signed (twoscomplement), covers value from -2,147,483,648 to 2,147,483,647.All numeric types in may be castinto other numerictypes(byte,short,long,float,double).

When lossy casts are done(e.g:intto byte), the conversion is donedepends to the length of thesmaller type.

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Primitive Type Descriptionlong 64 bits 8 bytes, signed (twos complement).

Ranges from-9,223,372,036,854,775,808 to+9,223,372,036,854,775,807

float 32 bits IEEE754-1985 4 bytes, IEEE 754. Covers a rangefrom 1.40129846432481707e-45 to3.40282346638528860e+38(posotive or negative).Like all numeric types, floats alsocan be cast into other numeric

types(byte,short,long,float,double).When lossy casts to integer type aredone(e.g:float to short), thefractional part is truncated andignored depends to the length of thesmaller type.

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Primitive Type Description

double 64 bits IEEE754-1985

8 bytes IEEE 754. Covers a rangefrom 4.94065645841246544e-324dTo 1.79769313486231570e+308d(positive or negative)

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Are the reserved words available in Javalanguage.

The functions of each of the keywords arepredefined.

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Types Keywords Data types, modifiers,class and access

specifiers

abstract, Boolean, byte,char, double, extends,

final, float, implements,import, int, inner, long,new, native, package,

private, protected, public,short, static, super, this,transient, var, volatile

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Types Keywords User defined data typesand type related

class, cast, instanceof,void, synchronized

Conditional if, else, switch, case,default

Flow control for, while, do, break,continue, goto and return

Exception handling Catch, finally, try, throw,throws

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Identify the keywords from the following:bytevariablegoodfor valuevoid

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1. Write a program to declare two variableshours_worked and pay_rate of integer data type and assign the values 8 and300. Print the value of the variableshours_worked and pay_rate.

2. Write a program to declare a variabletotal_classroom of integer data type andassign the value 30. Print the value.

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Is the conversion of a value of one datatype into another data type.Typecasting is of two types:

Implicit conversionExplicit conversion

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Implicit ConversionWhen a value of data type with lower range isassigned to a variable of data type with higher range.Java automatically makes the conversion.E.g :

double x; // Size is 8 byteint y=2; //Size is 4 bytesfloat z=2.2f;x=y+z;//Implicit conversion

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Explicit ConversionWhen a value of data type with higher rangeis assigned to a variable of data type withlower range, the user needs to make explicitconversion.

Explicit conversion leads to data loss.

E. g:int total_value;double book1 = 300.40;total_value=(int)book1; // Explicit conversion

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Write a Java program to declare a variabled of type double. Assign the value 102.5 to d . Declare a float variable fl . Assign thevalue of d to fl by performing an explicitconversion and print the value on thescreen.

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Is a symbol that instructs Java compiler toperform an operation, or action.Mathematical Operator :

Are operators that are used for performingsimple mathematical calculations such asaddition, subtraction, multiplication and

division.

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Write the resultant value of the followingexpressions.

Expression Result

14-4

14+4

14* 4

14/4

14%4

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Calculate the total marks for the given fivesubjects. Declare appropriate variables, assignvalues as given below, and calculate the total

marks:English = 85Maths = 100History = 75Geography = 70

Art = 85

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Assignment operatorExample 1

x = 3;

Syntax

= ;

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Assignment operatorExample 2

x = x + 3; x += 3;

Syntax

= ;

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Increment Operator

Increments the existing value by one.

Examplenum++;

Prefix :++a a=a+1; OR a+=1;

Postfix :a++ a=a+1; OR a+=1;

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Decrement Operator

Decrements the existing value by one.

Examplenum--;

Prefix :--a a=a-1; OR a-=1;

Postfix :a-- a=a-1; OR a-=1;

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Relational Operator Are used to perform a logical comparison of values,which results in a value that is either true or false .

Usually controls other statements

Used to compare data

Example

x = 10; x < 20;

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Operator Description Example

> Greater than a > b

< Less than a < b>= Greater than or equal to a >= b

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Expression Result

15 < 20.75 True

15 > 20.75 False

15 == 15 True

15 =20.75 False15 != 15 True

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Expression Result 4.5 = 0

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Logical Operator Are used to combine two or more logical expressionsto form a more complex logical expression.

To combine relational operator into better datatesting statements

Example

(number100)

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Operators Description

&& Logical AND

|| Logical OR

! Logical NOT

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Condition1 Condition2 && ||

true true true false

true false false true

false true false true

false false false false

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Conditional OperatorIs used to construct conditional expressions.

Exampleint aggregate = 95;char grade = (aggregate>90)?'A': 'B';

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Operator PresedenceDetermines the order in which mathematicalcomputations and operations are performed in

an expression.

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Result = a + b * 2 / c 5 \\a=b=5, c=2Result = 5 + 5 * 2 / 2 5Result = 5 + 10 / 2 5Result = 5 + 5 5Result = 10 5Result = 5.

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Is any combination of operators andoperands that evaluates to a value.The expressions can be classified into

three main categories:Numerical Expressions - Combine variables,numbers and mathematical operators.

Assignment Expressions - Assign values tovariables.Logical Expression - Results in true or false.

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S. No. a b c d Expression Result 1 24 2 8 - a/b-c

2 4 2 5 - a-b+c

3 2 4 2 1 a+b/c+d

4 3.5 2.0 - (a+b)*c

5 -34 6 - - a/b6 -34 6 - - a%b

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Next.Prepare for subtopic 2.2 Input and Output Stream