Fundamentals of Java|Java tokens.

In this article, what are Fundamentals of Java|Java tokens? is explained in detail. Tokens are different entities (individual units), using which we write java programs.These Fundamentals of Java|Java tokens. Java tokens are classified as follows.

Keywords

Keywords are special words or reserved words,which have special meaning and usage in a java program. Java supports 48 standard keywords,2 unused keywords and 3 literals.

(In total 53 keywords are supported in java).

Unused keywords are goto,const. (From the topic Fundamentals of Java|Java tokens?)

Literals are true,false,null.

48 standard keywords are.

Identifiers

Identifiers are entities,which are used to identify something uniquely in a program such as

• Class-name.
• Method-names.
• Data-member names.
• Variable Names.

Rules for identifiers

>They should start with alphabets or with $ symbol

>No space and no special characters should be present in between. However underscore "_" is allowed.

   Ex: Phone_number.

          First_number.

>We can use digits at the last .

   Ex: Subject1.

         Subject2.

>Keywords cannot be used as identifiers         (From the topic Fundamentals of Java|Java tokens?)

>Length of identifier can be 0 to 255 characters

  Ex: Permanent_address(17 characters)

>No two identifiers should be duplicated.

  Ex: int x,y;

        float x,y; 

by giving same variables for both data types leads to duplicating instead of using x,y use other variables like a,b.(i.e float a,b;) 

Constants (Literals)

Constants are fixed values of a particular type of data,which cannot be modified in a program. Technically they are known as literals.Java supports the following constants.

• Integers.
• Floating/Real numbers.
• Boolean.
• characters.
• String constant.

Integers: It supports three types of integers constants,they are (Decimal)10 (0-9), (Octal)8 (0-7), (Hexadecimal)16  (0-9,a,b,c,d,e,f).

Floating/Real Numbers: They are of two types     (From the topic Fundamentals of Java|Java tokens?)

Standard

Ex:3.1456

Scientific

Ex:3.14E+38

Boolean: They are two "True/False".

Characters: It is a single character which is represented in single quotations.

Ex:'A','\n','o' etc... 

String constant: It is a collection of characters represented in double quotations.

Ex:"hello","Welcome".

Note: In Java,we use "String" class to represent collection of characters.

Operators

Operators are special symbols,which are used to perform mathematical operations on values.

Ex: +,-,*,/,%,<,>,&,||,<<>>,etc..

Special Symbols

They are nothing but special characters only,with special usage and specific utility in a program.

Ex: . ; { } < > " ' [ ] etc..

Separators

These are used to separate some thing in a program based on situation.

Ex: . , ; { } space ( ) [ ] etc...   (From the topic Fundamentals of Java|Java tokens?)

Continue to next topic Fundamentals of Java|Data types.

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