1.
Identifiers :
Identifiers is a name assigned to the programming elements like variables,
method, class, abstract classes
Ex:-
>>int a=10;
>>intàdata
type
>>aà
variable
>>=à
Operator
>>10àConstant
>>;àSpecial Symbol
To use identifiers in java programs, java has provided
following rules and regulations.
1.
Identifiers must not be started with a numbers,
identifiers may start with an alphabet, _symbols, $ symbol, but the subsequent symbols may be a
number, an alphabet, _ symbol, $ Symbol.
Ex:-
>>int 9eno=111;àInvalid
>>String ename= “sai”;àValid
>>float emp9Sal= 900000.0f;àValid
>>String _empAddr= “Hyd”;àValid
>>float $esal=50000.0f;àValid
>>String emp_Qual= “B.tech”àValid
2.
Identifiers are not allowing all special
symbols, except _Symbol and $ symbol.
All Operators.
ex:-
>>String emp-Name= “Sai”;àInvalid
>>String emp_Addr= “Hyd”;àValid
>>String emp@Hyd= “Sai”;àInvalid
>>String #empAddr= “Hyd”;àInvalid
>>int emp.No=111;àInvalid
>>float emp+Sal=50000.0f;àInvalid
3.
Identifiers are not allowing space in the
middle,
Ex:-
>>for Name(“A”);àInvalid
>>forName(“A”);àValid
>>get Input Stream();àInvalid
>>getInputStream();àvalid
4.
Identifiers must not be duplicated within the
same scope, identifiers may be duplicated in two different scopes.
Ex:-
class A
{
int
i=10;
long
i=20;//Error
byte
j=40;
void
m1()
{
float
j=20.0f;
double
i=22.22;
short
j=30;// Error
}
}
5.
In java application s we can utilize all
predefined class names and interface names as identifiers
Ex:-
int Exception=10;
System.out.println(Exception);
Status:
No Compilation Error
Output
: 10
Date :29- july-2016
Ex:-
class A
{
public
static void main(String[] args)
{
String
String= "String";
System.out.println(String);
}
}
Status:
No Compilation Error
Output
: String
Ex:-
class A
{
public
static void main(String[] args)
{
int
System =10;
System.out.println(System);
}
}
Status: Compilation Error
Reasons
:- In java application, if we declare “System” as an integer variable then,
we must use System Integer Variable only
in the remaining part of the programming, we must not use Sytem as original class
name, if we use System as original class in the remaining programming then
compiler will rise an error.
In the above context, if we want to use
System has class Name then, we have to use fully qualified name of the classes.
Note:-
Specified class name and interface name
along with their package name is called “Fully Qualified Name”.
Ex:-
java.util.ArrayList
java.io.BufferedReader____etc
Ex:-
class Test
{
public
static void main(String[] args)
{
int
System=10;
java.lang.System.out.println(System);
System=System+10;
java.lang.System.out.println(System);
System=System+10;
java.lang.System.out.println(System);
}
}
Status
: No compilation Error
Output
: 10
20
30
Along with the above relations and
regulations
Java has provided the following suggestion
to use identifiers.
1.
In java
applications, it is suggestible to provide identifiers with a particular
meaning
Ex:-
String xxx= “abc123;àNot
Suggestible
String accNo= “abc123”àSuggestible
2.
No length restriction for the identifiers in
java applications ,but, it is suggestible to provide length of the identifiers
around 10 Symbols.
Ex:-
String temporaryemployeeaddress= “ Hyd”;àNot
suggestible
String tempEmpAddr= “Hyd”;àSuggestible
3.
If we have multiple words within a single
identifiers then it is suggestible to separate multiple word with the special
notations like “_” systems.
Ex:-
String tempEmpAddr= “Hyd”;àNot
Suggestible
String temp_Emp_Addr= “Hyd”àSuggestible
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