Tokens in Java

Token is a smallest unit of java which is very important without token, we cannot write any java program.

Token is classified into 4 types:

1. Keywords

2. Identifiers

3. Separators

4. Literals

Keywords:

• Keywords are predefined words

• Keywords has it's own task

• They are reserved words

• We can use keywords, but we can't modify it.

• Keywords are written in lowercase.

• They are 50+ keywords. (around 67 )

• E.g. public, class, static, void, etc.

Identifiers:

• A name given by a programmer to the components of java

• E.g. program name, class name, variable name, etc.

• Rules to follow while writing Identifier:

  1. Identifiers should not start with the numbers; but we can see the number in between the identifier or in the end of the identifier; which is known as alphanumeric.

  2. We cannot use any special character except dollar($) and underscore(_)

  3. Character space is not allowed in identifier

  4. We cannot write keyword as an identifier

Separators:

Separators are used to separate the set of instruction. E.g. {}, [], (), :, ;

Literals:

• Literals are the value/ data which we use in java program to perform a task

• Literals are classified into

  1. Primitive Literal

  2. Non- Primitive Literal

1. Primitive Literal:

   The primitive literal is classified into following types

   e.g.

   1. Number Value:

      Integer e.g. 100, 5008

      Float e.g. 10.55, 12.9, 15.3

   2. Character Value:

      Anything which is enclosed in a single quote

      e.g. 'c', '1', 't', '@'

   3. Boolean Value:

      It is used for condition making.

2. Non - Primitive Literal:

   The address or reference of an object is known as non-primitive literal/ non-primitive value.

   e.g. String

   Any value which is enclosed in a double quotes

   Doesn't have a size limit.