Variables/Identifiers in Java Part . 8

Variables/Identifier in Java

Identifiers are used in java program for Identification purpose.

Whatever the name we are using in java program is called as Identifier It can class Name , Method Name, Variable Name.

Question = Why we use Identifiers?

Answer = TO Identification purpose.

1 – The valid characters in java Identifiers are :

       a – z, A – Z, 0 – 9, underscore (_), dollar symbol ($).

2 – Identifiers should not start from Digit :

      xyz11      [valid]

      11xyz      [invalid]

3 – No length Restriction but choose short name as Identifiers.

4 – Java Identifiers are case sensitive.

5 – we can’t use keywords/reserved word as Identifiers.

       int if=10;              [invalid]

       int double=10;    [valid]

       class class=10;     [invalid]

 6 – All predefine classes and Identifiers are allowed to use as Identifiers.

       int system=10;

       string string=”xyz”;

       int Runnable=30;      //valid Runnable is predefined interface.   

Note :- from java 9 version on word  ,_(underscore) is keyword then we can not use as Identifier.

Ex – int_=10;  (java 8)is valid.

        int_=10;  (java 8)is invalid.

       We can’t  say keywords as identifiers.

Question = Which of following valid identifiers in java 11?

Answer = int _a=15;            [valid]

                  Int __d=30;          [valid]

                  int _=35;               [invalid]

How many identifiers are present in this program ——

Total five identifiers in this program (Test, main, string, ar, x)

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