Java Variable Types: A Beginner's Guide | Exercises Java Programming

Java - Variable Types

A variable provides us with named storage that our programs can manipulate. Each variable in Java has a specific type, which determines the size and layout of

the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.

You must declare all variables before they can be used. Following is the basic form of a variable declaration −

data type variable [ = value][, variable [ = value] ...] ;

Here

Here data type

data type is one of Java's datatypes and

is one of Java's datatypes and variable

variable is the name of the variable. To declare more than one variable of the specified type, you can use a comma-

is the name of the variable. To declare more than one variable of the specified type, you can use a comma-

separated list.

Following are valid examples of variable declaration and initialization in Java −

Example

int

int a

a,

, b

b,

, c

c;

;

// Declares three ints, a, b, and c.

int

int a

a =

=

10

10,

, b

b =

=

10

10;

;

// Example of initialization

byte

byte B

B =

=

22

22;

;

// initializes a byte type variable B.

double

double pi

pi =

=

3.14159

3.14159;

;

// declares and assigns a value of PI.

char

char a

a =

=

'a'

'a';

;

// the char variable a iis initialized with value 'a'

This chapter will explain various variable types available in Java Language. There are three kinds of variables in Java −

Local variables

Instance variables

Class/Static variables

Local Variables

Local variables are declared in methods, constructors, or blocks.

Local variables are created when the method, constructor or block is entered and the variable will be destroyed once it exits the method, constructor, or

block.

Java Variable Types: A Beginner's Guide, Exercises of Java Programming

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Java - Variable TypesJava - Variable Types

A variable provides us with named storage that our programs can manipulate. Each variable in Java has a specific type, which determines the size and layout of

A variable provides us with named storage that our programs can manipulate. Each variable in Java has a specific type, which determines the size and layout of

the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.

the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.

You must declare all variables before they can be used. Following is the basic form of a variable declaration −

You must declare all variables before they can be used. Following is the basic form of a variable declaration −

Here

Here

data type

data type

is one of Java's datatypes and

is one of Java's datatypes and

variable

variable

is the name of the variable. To declare more than one variable of the specified type, you can use a comma-

is the name of the variable. To declare more than one variable of the specified type, you can use a comma-

separated list.

separated list.

Following are valid examples of variable declaration and initialization in Java −

Following are valid examples of variable declaration and initialization in Java −

ExampleExample

a

b

B

a

This chapter will explain various variable types available in Java Language. There are three kinds of variables in Java −This chapter will explain various variable types available in Java Language. There are three kinds of variables in Java −

Local variables

Local variables

Instance variables

Instance variables

Class/Static variables

Class/Static variables

Local Variables

Local Variables

Local variables are declared in methods, constructors, or blocks.

Local variables are declared in methods, constructors, or blocks.

Local variables are created when the method, constructor or block is entered and the variable will be destroyed once it exits the method, constructor, or

Local variables are created when the method, constructor or block is entered and the variable will be destroyed once it exits the method, constructor, or

block.

block.

Access modifiers cannot be used for local variables.

Access modifiers cannot be used for local variables.

Local variables are visible only within the declared method, constructor, or block. Local variables are visible only within the declared method, constructor, or block.

Local variables are implemented at stack level internally. Local variables are implemented at stack level internally.

There is no default value for local variables, so local variables should be declared and an initial value should be assigned before the first use.

There is no default value for local variables, so local variables should be declared and an initial value should be assigned before the first use.

Here,Here, ageage is a local variable. This is defined insideis a local variable. This is defined inside pupAge()pupAge() method and its scope is limited to only this method.method and its scope is limited to only this method.

age

age

[])

test

This will produce the following result −This will produce the following result −

Following example uses

Following example uses

age

age

without initializing it, so it would give an error at the time of compilation.

without initializing it, so it would give an error at the time of compilation.

Instance variables can be accessed directly by calling the variable name inside the class. However, within static methods (when instance variables are

Instance variables can be accessed directly by calling the variable name inside the class. However, within static methods (when instance variables are

given accessibility), they should be called using the fully qualified name.

given accessibility), they should be called using the fully qualified name.

ObjectReference.VariableName

ObjectReference.VariableName

name

salary

empOne

This will produce the following result −This will produce the following result −

Class variables also known as static variables are declared with the static keyword in a class, but outside a method, constructor or a block.

Class variables also known as static variables are declared with the static keyword in a class, but outside a method, constructor or a block.

There would only be one copy of each class variable per class, regardless of how many objects are created from it.

There would only be one copy of each class variable per class, regardless of how many objects are created from it.

Constant variables never change from their initial value.

Constant variables never change from their initial value.

Static variables are created when the program starts and destroyed when the program stops. Static variables are created when the program starts and destroyed when the program stops.