Identifiers in java

A Name in Java program is called Identifiers. User-defined words in our java program is called Identifiers
It can be a class name or method name or variable name or label name. Example:

class Test{
public static void main(String arr[]){
int myVariable=56;
System.out.println("Identifier Test");

In above example Class Name{Test} ,Variable name {myVariable} ,String array name {arr} are the identifiers. These words are defined by programmer.

Rules for defining the identifiers-

There are few rule which we have to follow while declaring the identifier-

  The only allowed character in java Identifiers are-

A - Z
a - z
0 - 9

  If we are using any other character apart from above mention characters, we will get compile time error.

  An identifier cannot start with the digit.

  Identifiers can be any combination of digit and alphabets but not start from digit.

  Keywords cannot be used as identifiers.

  identifiers are case Case-Sensitive

  There is no length limit for java identifiers but it is recommended to not use an identifier of more than 15 characters.

  All pre-defined java class Names and interface name can be used as an identifier. But it's not recommended to use.

//program for creating valid and invalid identifiers
class Identifier
public static void main(String[] args) {
	int x=56;//valid identifier
	int Ab=54;//valid identifier;
	int _ab=45;//valid identifier;
	int $_test=11;//valid identifier;
	//int 4ab=54;  //invalid identifier// can't be start from digit
	//int [email protected]=65; //invalid //@ can't be used
	int Runnable=76;
	System.out.println("Runnable= "+Runnable); 


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