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Variable And Type Data


Language of programming in general, recognizing the existence of variable used for save assess or data. While Java alone known as language of programming with nature of typed strongly with the meaning obliged data type declaration from all variable, and if forgetting or wrong follow variable declaration order, hence will get error at the (time) of process compiles.



  1. Type Data

Java have data type able to be categorized to become two group, that is primitive data type and reference.

1. Primitive Type Data

Eight kinds of primitive data type in programming of Java, that is :

    • Integer (Integer )

Integer represent data type of numeric used if do not deal with number or fraction denary. Integer number usually use int, and non byte, and also short of long. Integer number also recognize positive value and negativity (number signed). Data type of byte and of short only used at special application which pay attention usage of memory. While long seldom be used by because seldom need number equal to capacities of long.

    • Floating Point (Number Fraction)

Floating Point used to handle number denary or more calculation of detail compared to integer.

    • Char

Char is single character which defined with early and terminated with sign ‘ (pluck single). Char differ with String, because String not such a primitive data type, but have represented a object. type of Char follow order Unicode, so that can use code / u is then followed number from 0 until 65535, but which commonly use is number of hexadecimal from 0000 until FFFF.

    • Boolean

In Java recognized by data type of Boolean which consist of two value just, that is and true of false. Boolean of vital importance in evaluating an condition and is often used to determine program path.

2. Type Data Reference

Excess of programming orient object is can define new data type which represent object of certain class. this Data type is used for the reference of or object of class certain, like String.

  1. Variable

Variable represent container used for save an value at a program with certain type. To define variable, we earn to use identifier to name the variable.

1. Identifier

Identifier is character corps able to be used to naming variable, method, class, interface, and package. As language of program in general, Java have regulation for valid or valid identifier. Identifier can be referred as valid or valid if early with :

    • Letter / alphabet
    • Currency character
    • Underscore (_)

Identifier can consist of :

    • Letter / alphabet
    • Number
    • Underscore (_)

Identifier may not contain @, space or early with number. Besides, identifier may not use or keyword of words owning meaning or used in programming of Java. Lists keyword java :

    • Abstract
    • Double
    • Int
    • strictfp
    • Boolean
    • Flse
    • Static
    • super
    • break
    • fxtends
    • long
    • switch
    • byte
    • final
    • native
    • synchronized
    • case
    • finally
    • new
    • this
    • catch
    • float
    • package
    • throw
    • char
    • for
    • private
    • throws
    • class
    • goto
    • protected
    • transient
    • const
    • if
    • public
    • try
    • continue
    • implements
    • return
    • void
    • default
    • import
    • short
    • volatile
    • do
    • instanceof
    • interface
    • while

Besides using ordinary character, we also can use Unicode as identifier.

2. Declaration Variable

Elementary Syntax :

[data type] [name of variable]

After variable declaration with data type, hereinafter assigning value the variable with sign =. Earn also declaration and assign value in a line. We earn to make variable become constant which cannot be altered by its value by enhancing keyword before data type of variable. So that this constant can be accessed by other class without having to making object beforehand, hence we earn to enhance modifier and public of keyword static.


Language of programming in general, recognizing the existence of variable used for save assess or data. While Java alone known as language of programming with nature of typed strongly with the meaning obliged data type declaration from all variable, and if forgetting or wrong follow variable declaration order, hence will get error at the (time) of process compiles.



  1. Type Data

Java have data type able to be categorized to become two group, that is primitive data type and reference.

1. Primitive Type Data

Eight kinds of primitive data type in programming of Java, that is :

    • Integer (Integer )

Integer represent data type of numeric used if do not deal with number or fraction denary. Integer number usually use int, and non byte, and also short of long. Integer number also recognize positive value and negativity (number signed). Data type of byte and of short only used at special application which pay attention usage of memory. While long seldom be used by because seldom need number equal to capacities of long.

    • Floating Point (Number Fraction)

Floating Point used to handle number denary or more calculation of detail compared to integer.

    • Char

Char is single character which defined with early and terminated with sign ‘ (pluck single). Char differ with String, because String not such a primitive data type, but have represented a object. type of Char follow order Unicode, so that can use code / u is then followed number from 0 until 65535, but which commonly use is number of hexadecimal from 0000 until FFFF.

    • Boolean

In Java recognized by data type of Boolean which consist of two value just, that is and true of false. Boolean of vital importance in evaluating an condition and is often used to determine program path.

2. Type Data Reference

Excess of programming orient object is can define new data type which represent object of certain class. this Data type is used for the reference of or object of class certain, like String.

  1. Variable

Variable represent container used for save an value at a program with certain type. To define variable, we earn to use identifier to name the variable.

1. Identifier

Identifier is character corps able to be used to naming variable, method, class, interface, and package. As language of program in general, Java have regulation for valid or valid identifier. Identifier can be referred as valid or valid if early with :

    • Letter / alphabet
    • Currency character
    • Underscore (_)

Identifier can consist of :

    • Letter / alphabet
    • Number
    • Underscore (_)

Identifier may not contain @, space or early with number. Besides, identifier may not use or keyword of words owning meaning or used in programming of Java. Lists keyword java :

    • Abstract
    • Double
    • Int
    • strictfp
    • Boolean
    • Flse
    • Static
    • super
    • break
    • fxtends
    • long
    • switch
    • byte
    • final
    • native
    • synchronized
    • case
    • finally
    • new
    • this
    • catch
    • float
    • package
    • throw
    • char
    • for
    • private
    • throws
    • class
    • goto
    • protected
    • transient
    • const
    • if
    • public
    • try
    • continue
    • implements
    • return
    • void
    • default
    • import
    • short
    • volatile
    • do
    • instanceof
    • interface
    • while

Besides using ordinary character, we also can use Unicode as identifier.

2. Declaration Variable

Elementary Syntax :

[data type] [name of variable]

After variable declaration with data type, hereinafter assigning value the variable with sign =. Earn also declaration and assign value in a line. We earn to make variable become constant which cannot be altered by its value by enhancing keyword before data type of variable. So that this constant can be accessed by other class without having to making object beforehand, hence we earn to enhance modifier and public of keyword static.


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