Java – Java Variable Types

In Java all variables must be declared before the use.basic declaration will be like,

Syntax:

‘ DataType VariableName; ‘

Example:

int a;

float b;

Continuous declaration also allowed like ‘int a,b,c;’.

There are three types of variables in java.they are,

  • Local Variable.
  • Instance Variable.
  • Class/Static Variable.

Local Variable:

  • Local variables are declared inside the method,constructor or block.
  • They are visible only inside the block in which they are declared.
  • Local variables do not have a default value so it must be declared  and initialized before the first use.
  • Access modifiers cannot be implemented for local variables.
  • Local variables are destroyed immediately after exits the block.

Example Code:

public class Age {

public void printAge()

{

int ageCount = 0;        // ageCount is a Local Variable

ageCount = ageCount + 5;

System.out.println(“Age is “+ageCount);

}

public static void main(String args[])

{

Age object1 = new Age();

object1.printAge();

}

}

Instance Variable:

  • Instance variables are declared outside the method and constructor or block.
  • Memory will be created in the heap when the instance variable is created.
  • Instance variable is created when an object is created using the ‘new’ keyword.
  • Access modifiers can be applied to these variables.but however ‘private’ is advisable.If the variables needs to be accessed by the subclasses then the visibility can be modified.
  • Instance variables have their default values.So it is not a must to declare and instantiate.Example: int a;
    Here the variable ‘a’ holds 0 as its default value.
  • Instance variables holds values that must be referenced by more than one method,constructor or block.State should be maintained throughout the class.
  • They can be directly called by their name inside the class.Subclasses have to use the qualified name.Example: ‘ObjectName.VariableName’

Example Code:

public class Employee {

public String employeeName;     // employeeName and employeeSalary are Instance Variables

public int employeeSalary;

public Employee(String name)

{

employeeName = name;

}

public void setEmployeeValues(int pay)

{

employeeSalary = pay;

System.out.println(“Employee Name is “+employeeName+” and Employee Salary is “+employeeSalary);

}

public static void main(String args[])

{

Employee employee = new Employee(“Manishankar”);

employee.setEmployeeValues(50000);

}

}

Class/Static Variable:

  • Class variables are also called as Static variables.Variables are declared with a ‘Static’ keyword outside the method,constructor or block.
  • There will be only one copy of the static variable.
  • Static variables can have access modifiers.
  • Static variables starts when the program starts and destroyed when the program stops.
  • Static variables have static memory.
  • Static variables can be accessed by calling the variable with its class name.Example: ‘ClassName.VariableName’

Example Code:

public class Test {

// Salary is a private static variable

private static int salary;

// Name is a constant variable

private static final String name = “Manishankar”;

public static void main(String args[])

{

salary = 50000;

System.out.println(“Salary is “+salary+” and Name is “+name);

}

}

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