Data Types: There are two types of data types –

  • Primitive Data type
  • Non Primitive Data type

datatypes
Primitive Data Types
These are the predefined data types. In java there are 8 primitive data types which are as follows:

Data Types Default Values Range Default Size Example
boolean False True/ False 1bit boolean b = True
char ‘\u0000’ ‘\u0000’ to ‘\uffff’ 2byte char c=’A’
byte 0 -128  (-2^7) to 127 (2^7 -1) 1byte byte  b = 12
short 0 -32,768 (-2^15)  to  32,767(2^15 -1) 2byte short s=1000
int 0 – 2,147,483,648 (-2^31)  to 2,147,483,647(2^31 -1) 2byte int i= 100000000
long 0L -9,223,372,036,854,775,808(-2^63)  to 9,223,372,036,854,775,807(2^63 -1) 8byte long l= 1000000L
float 0.0f Single-precision 32-bit IEEE 754 floating point 4byte float f = 25.9f
double 0.0d Double-precision 64-bit IEEE 754 floating point 8byte double d = 152.3

Variable: A variable is a memory address that can change and when memory address cannot change then it is known as constant. Variable is a name of the memory location where data is stored. Once a variable is stored then space is allocated in memory. It defines a variable using a combination of numbers, letters and the underscore character.
There are three types of variables: Local, Instance and Static

Learn Java

Local Variable: A variable we declared inside of method called as Local variable.
e.g.

public class intellipaatclass
{
public void method()
{
int a = 10;  // Local Variable
}
}

Instance Variable: A variable we declared inside of class but outside of method is called instance variable. It is not declared as static.
e.g.

public class intellipaatclass
{
int a = 10;  // Instance Variable
public void method()
{
}
}

Static Variable: A variable that we declared as static is called static variable. It cannot be local.
e.g.

public class intellipaatclass
{
static int a = 10;  // Static Variable
public void method()
{
}
}

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