TOKENS

The tokens are the small building blocks of a Java program that are meaningful to the Java.

TYPES OF TOKENS:

Keywords
Data types
Literals
Operators
Separators
Comments
Identifiers

1. KEYWORDS:

Keywords are reserved words.

keywords are used to perform specific action.

There are approximately 50 keywords.

RULES FOR KEYWORDS:

All keywords are just a single word.
All keywords are in lower case.

LIST OF KEYWORDS:

DATA TYPES:

Data type specify the size and type of the data.

IDENTIFIERS:

Identifiers are case sensitive.

It is nothing but a sequence of one or more character, there is no maximum length.

Identifiers cannot starts with digits [0 – 9].

Obviously it should follow rules else will result in error.

Keywords shouldn’t be used as identifiers.

$(dollar) and _ (underscore) is only used, no other special character are allowed.

LITERALS:

Any constant value which can be assigned to the variable is called literal/constant.

Integral literals: An integer literal is a numeric value (associated with numbers) without any fractional or exponential part. Integer literals are sequences of digits.

There are three types of integer literals:

Decimal Integer: These are the set of numbers that consist of digits from 0 to 9. It may have a positive (+) or negative (–) Note that between numbers commas and non-digit characters are not permitted. For example, 5678, +657, -89, etc.

Octal Integer: It is a combination of number have digits from 0 to 7 with a leading 0. For example, 045, 026, etc.

Hexa-Decimal: The sequence of digits preceded by 0x or 0X is considered as hexadecimal integers. It may also include a character from a to f or A to F that represents numbers from 10 to 15, respectively. For example, 0xd, 0xf, etc.

Character literals:

Character (Char) literals are expressed as an escape sequence or a character, enclosed in single quote marks, and always a type of character in Java.

Example: ‘a’ , ‘e’ , ‘o’ , etc…

String literals:

String literals are sequences of characters enclosed between double quote (“”) marks. These characters can be alphanumeric, special characters, blank spaces, etc.

Boolean literals:

Boolean literals have only two values and so are divided into two literals:

True represents a real boolean value
False represents a false boolean value

So, Boolean literals represent the logical value of either true or false. These values aren’t case-sensitive and are equally valid if rendered in uppercase or lowercase mode. Boolean literals can also use the values of “0” and “1.”

Example: true , false

Comments:

Single line comment – //

Multi line comment- /* */

Separator:

Separators help us defining the structure of a program.

; —–> Single line separator, technically called as terminator.

{} —–> Multi line separator, technically called as block.

Operators:

Operators are reserved symbols.

Every operator has a specific action to perform.

Types of operators:

Arithmetic operator:

Arithmetic operators are used to perform simple mathematical operations.

Logical operator:

Logical operators are used for performing the operations on one or two variables for evaluating and retrieving the logical outcome.

Relational operator:

The Relational operators compare between operands and determine the relationship between them.

Operator	Meaning
==	Is equal to
!=	Is not equal to
>	Greater than
<	Less than
>=	Greater than or equal to
<=	Less than or equal to

Conditional operator:

Condition is a statement which gives either true or false.

(condition ? true : false ) ——–> eg: (9 > 7 ? 9 : 7)

Checks the condition whether true or false, if it is true then it will print the number before colon else it will print after colon.

Expression: Combination of operands and operators. eg: a + b, a > b , a == b , a – b.

Condition: All conditions are expressions, but not all expressions are conditions. The combination of operands and operators which gives o/p as value then we can’t use in condition. (NOTE: Can’t use arithmetic operators)

Assignment operators:

Assings the value to a variable.

Initialize: int a = 5; ——-> 5 is assigned to a

Reassign: a=15; ——-> New value is 15