Core Java

Language fundamentals 

Agenda :

1. identifiers

2. Reserved word

3.Data Types

4. Literals 

5. Array

6. Types of Variables

7. var-arg method

8. main method

9. command line arguments

10. java coding standard

======================================================

1. Identifiers : a name in java program is called identifier which can be used for identification purpose.it can be method name, class name, variable name or label name.

class Test 

{

public static void main(String args[])

{

int x=10;

}

}

Q1. how many identifiers?

Answer : 5

Rules for defining java identifiers

1. the only allowed characters are - A to Z , a to z, 0 to 9, $ , _

total_number ?

total# ?

2. identifiers cant start with digit

total123 ?

123total ?

3. java identifiers are case sensitive (java language is case sensitive)

int number =10

int Number =20

int NUMBER =30

4.there is no length limit for java identifier but it is not recommended to take too lengthy identifier

5 we cant use reserve words as identifiers

int x =10 ?

int if =20 ?

6. all predefined class name and interface name can be used as identifier but it is not recommended.

Which of the following valid java identifiers?

total_number

total#

123total

total123

ca$h

_$_$_$

all@hands

java2Share

Integer

Int

int

=====================================================

Reserve words(53)

in java some words are reserved to represent some meaning or functionality , such type of words are called reserved words.

3 Literals (true , false , null)

50 keywords- used 48 unused (goto,const)

keywords for data types

1. byte 

2. short 

3. int

4. long

5. float

6.double

7. boolean

8. char

keywords for flow control

if

else

switch

case

default

while

do

for

break

continue

return

keywords for modifiers

public

private

protected

static 

final

abstract

synchronized

native

strictfp

transient

volatile

keywords for exception handling

try

catch

finally

throw

throws

assert

class related keywords

class

interface

extends

implements

package

import

object related keywords

new

instanceof

super

this

return type keyword

void

"in java return type is mandatory if a method wont return anything then we have to declare that method with void return type.

but in c language return type is optional and default return type is int"

unused keywords

goto 

const

reserved literal

true

false

null

enum keyword - we can use enum for named constant

Conclusion - only lowercase , only alphabets 

Which list contain valid java identifiers?

new, delete

goto, constant

break , continue, return,exit

final, finally,finalize

throw, throws , thrown

notify, notifyAll

implements, extends, imports

sizeof, instanceof

instanceOf,strictFp

byte,Short,Int

Which of the following are java reserved words

public 

static

void

main

String

args

None of the above