Java Tokens

 

  Java tokens are smallest individual units in a program

 

 

                                                                          

Keywords: 

•        These are the pre-defined reserved words of any programming language.

•         Each keyword has a special meaning.

•         It is always written in lowercase.

e.g. class, while, for, interface, abstract…..

Identifier:

•         Identifiers are used to name a variable, constant, function, class, and array.

•         It is usually defined by the user.

•        It uses letters, underscores, or a dollar sign as the first character.

•        Identifier names must be different from the reserved keywords.

 

There are some rules to declare identifiers are:

❑     The first letter of an identifier must be a letter, underscore or a dollar sign. It cannot start with digits but may contain digits.

❑     The whitespace cannot be included in the identifier.

❑     Identifiers are case sensitive.

•        Some valid identifiers are:

•         PhoneNumber  

•        PRICE  

•        radius  

•        a  

•        a1  

 Invalid Identifiers

•        1sum

•        Sum 1

 

Literals: 

•        literal is a notation that represents a fixed value (constant) in the source code.

•        It can be categorized as an integer literal, string literal, Boolean literal, etc.

•        It is defined by the programmer.

•        Once it has been defined, it cannot be changed.

Java provides five types of literals are as follows:

●      Integer

●      Floating Point

●      Character

●      String

●      Boolean

Operators: 

•        operators are the special symbol to perform mathematical operations or logical manipulations

•        Java provides different types of operators that can be classified according to the functionality they provide.

There are eight types of operators in Java, are as follows:

•        Arithmetic Operators

•        Assignment Operators

•        Relational Operators

•        Unary Operators

•        Logical Operators

•        Ternary Operators

•        Bitwise Operators

•        Shift Operators

Separators: 

•        The separators in Java is also known as punctuators.

•         separators in Java, are as follows:

•        ; (semicolon)

•        , (comma)

•        . (dot)

•        { } (braces)

•        [ ] (bracket)

•        ( ) (parenthesis)

 

Comments:

Comments are used to describe the program

•         Single Line Comment (// Double Slash)

// This is an example program to add two numbers

// Java program to illustrate the addition of numbers

 

•          Multi-line Comment (/*     */)

/*This is an example

 program to

add two numbers */

Constants

❑      Constants are the fixed values that never change during the execution of a program.

❑       Various types of constants:

⮚      Integer Constants

▪         An integer constant is nothing but a value consisting of digits or numbers

▪         Example : 111, 1234

⮚      Floating point Constants

▪         constants that contain a decimal point or a fraction value. 

▪         Example: 223.14, 400.054

⮚      Character Constants

▪         A character constant contains only a single character enclosed within a single quote (‘ '). 

▪         Example: ‘A’ , ‘m’, ‘9’

⮚      String Constants

▪        A string constant contains a sequence of characters enclosed within double quotes (“ “).

▪         Example: “Welcome”, “Hello”