Types of variables in Java
There are three types of variables that can be used in Java. Let us go through each of them in detail.
Local variables
The variables declared in methods or constructors used only inside that code block are known as local variables. These variables can not be accessed outside their declared method or block. A block refers to a set of code that is enclosed within curly brackets { }. Local variables are used only when the program is running and discarded after exiting its block. Here is an example to show the scope of local variables in a program.
class A
{
public static void main(String[] args)
{
int a = 10;
if (a > 5)
{
int b = 10;
a = a + b;
}
System.out.println(a,b);
}
}
You can also try this code with Online Java Compiler
Output:
error: cannot find symbol
System.out.println(a,b);
^
symbol: variable b
location: class A
The variable ‘a’ is local to the main method, and variable b is local to the if block. We get an error since the print statement attempts to access the value to b from outside the if block.
Static variables
Static, a non-access modifier in Java, is attached as a prefix to variables or methods to indicate that it belongs to the entire class and not just an object. In other words, static members of a program can be accessed without creating an object. All objects of a class share a single copy of the static variable. Hence, they are also known to be global variables. However, their scope is limited to the declared class and not outside. Static members are allocated their memory only once when the entire class is loaded for execution.
public class Main
{
static int a = 10;
public static void main(String[] args)
{
int b = 10;
System.out.prinln(a)
sum(b);
}
public static void sum(int num)
{
System.out.println(a+num);
}
}
You can also try this code with Online Java Compiler
Output:
10
20
Variable ‘a’ is a static variable and can be accessed in the main and sum methods. Since ‘b’ is a local variable, it is passed to the sum function as a parameter.
Instance Variables
Classes and methods are essential parts of a Java program. Instance variables are declared in a class outside any method, constructor, or block. Unlike local variables, instance variables directly form a part of the class and have default values. Access modifiers are used to declare instance variables. Instance variables can form a part of several subroutines, i.e. even if the value of an instance variable is situated in one subroutine, it can be used while executing another subroutine. However, they can be accessed only using objects.
In the given example, ‘a’ is an instance variable visible to any child class. It is accessed using the ‘obj’ object.
public class A
{
public int a;
public A (int b)
{
a = b;
}
public void display()
{
System.out.println(a);
}
public static void main(String args[])
{
A obj = new A(10);
obj.display();
}
}
You can also try this code with Online Java Compiler
Output:
10
Must Read Conditional Statements in Java and Swap Function in Java
Frequently Asked Questions:
What is a variable -- in Java?
A variable in Java is a container that holds data values which can be changed during program execution.
What are the 4 variables in Java?
Java has four types of variables: local, instance, static (class), and parameter variables, each with its own scope and purpose.
How to name Java variables?
Java variable names should start with a letter, use camelCase, avoid spaces/symbols, and should not use reserved keywords.
What is a variable in programming?
In programming, a variable stores data that can be used, modified, or updated throughout the program as needed.
Conclusion
Variables carry the most important part of any program: the data. Without variables, it is impossible to perform even basic arithmetic operations. This blog covers the basics of variables in Java and how to use them in a program. It also explains the different kinds of variables in Java examples to help understand them better.
Related Links:
Addition of two numbers in java
Static and Instance Methods in Java
What is static in Java?
Classes and Objects in Java
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