Easy way to Identify ?

Identifier: A name in java program is called identifier. It may be class name, method name,
variable name and label name.
Example:
Rules to define java identifiers:
Rule 1: The only allowed characters in java identifiers are:
1) a to z
2) A to Z
3) 0 to 9
4) _
5) $
Rule 2: If we are using any other character we will get compile time error.
Example:
1) total_number-------valid
2) Total#------------------invalid
Rule 3: identifiers are not allowed to starts with digit.
Example:
1) ABC123---------valid
2) 123ABC---------invalid
Rule 4: java identifiers are case sensitive up course java language itself treated as case sensitive
language.
class Test{
int number=10;
int Number=20;
int NUMBER=20; we can differentiate with case.
int NuMbEr=30;
}]
Rule 5: There is no length limit for java identifiers but it is not recommended to take more than
15 lengths.
Rule 6: We can’t use reserved words as identifiers.
Example: int if=10; --------------invalid
Rule 7: All predefined java class names and interface names we use as identifiers.
Example 1:
class Test
{
public static void main(String[] args){
int String=10;
System.out.println(String);

}}
Output:
10
Example 2:
class Test
{
public static void main(String[] args){
int Runnable=10;
System.out.println(Runnable);
}}
Output:
10
Even though it is legal to use class names and interface names as identifiers but it is not a good
programming practice.

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