Variable and Datatype and Operators in java

Variable and Datatype in Java

1. Variable
2. Types of Variable
3. Data Types in Java

In this page, we will learn about the variable and java data types. Variable is a name of memory location. There are three types of variables: local, instance and static. There are two types of datatypes in java, primitive and non-primitive.

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Variable

Variable is name of reserved area allocated in memory.

1    int data=50;//Here data is variable  

Types of Variable

There are three types of variables in java ·         local variable ·         instance variable ·         static variable

Local Variable

A variable that is declared inside the method is or constructor or static or initializer block called local variable. Local variable cannot have public, private, protected and default. Local variable must initialize before use. Scope of local variable only inside the methods or constructors or block where it is declare.

Instance Variable

A variable that is declared inside the class but outside the method is called instance variable . It is not declared as static.

Static variable

A variable that is declared as static is called static variable. It cannot be local.

We will have detailed learning of these variables in next chapters.

Example to understand the types of variables

1.    class A{  

2.    int data=50;//instance variable  

3.    static int m=100;//static variable or class   variable

4.    void method(){  

5.    int n=90;//local variable  

6.    }  

7.    }//end of class  

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Data Types in Java

Data types defines the type of data.

In java, there are two types of data types ·         primitive data types ·         non-primitive data types

Data Type	Default Value	Default size
boolean	false	1 bit
char	'\u0000'	2 byte
byte	0	1 byte
short	0	2 byte
int	0	4 byte
long	0L	8 byte
float	0.0f	4 byte
double	0.0d	8 byte

Why char uses 2 byte in java and what is \u0000 ?

because java uses unicode system rather than ASCII code system. \u0000 is the lowest range of unicode system.To get detail about Unicode see below.

Unicode System

Unicode is a universal international standard character encoding that is capable of representing most of the world's written languages.

Why java uses Unicode System?

Before Unicode, there were many language standards:

·         ASCII (American Standard Code for Information Interchange) for the United States. ·         ISO 8859-1 for Western European Language. ·         KOI-8 for Russian. ·         GB18030 and BIG-5 for chinese, and so on.

This caused two problems: 1.    A particular code value corresponds to different letters in the various language standards. 2.    The encodings for languages with large character sets have variable length.Some common characters are encoded as single bytes, other require two or more byte.

To solve these problems, a new language standard was developed i.e. Unicode System.

In unicode, character holds 2 byte, so java also uses 2 byte for characters.

lowest value:\u0000

highest value:\uFFFF

Operators in java

Operator in java is a symbol that is used to perform operations. There are many types of operators in java such as unary operator, arithmetic operator, relational operator, shift operator, bitwise operator, ternary operator and assignment operator.

Operators	Precedence
postfix	expr++ expr--
unary	++expr --expr +expr -expr ~ !
multiplicative	* / %
additive	+ -
shift	<< >> >>>
relational	< > <= >= instanceof
equality	== !=
bitwise AND	&
bitwise exclusive OR	^
bitwise inclusive OR	|
logical AND	&&
logical OR	||
ternary	? :
assignment	= += -= *= /= %= &= ^= |= <<= >>= >>>=