45. Variable Declaration and Initialization

The variable is a basic unit of storage in a Java Program.

Declaring a Variable: In Java, all the programs must be declared before they can be used. Program to demonstrate what happens when we use a variable without declaring it: class VariableNotDeclared {    public static void main(String args[])    {         a=5;    //Using a variable without declaring it         System.out.println(a);    }  } Output of this program: Error. "Cant find the symbol a . Symbol: Variable a  Location: VariableNotDeclared"  This error is displayed because we've not declared the variable a.

Program to demonstrate that we can declare more than one variable of same type in a single statement class MultiDeclarationsSingleStatement {    public static void main(String args[])    {       int a,b,c;    //Here I've delcared three variables a,b and c as int data type in a single statement         a=3;       b=4;       c=5;         System.out.println("a:"+a);       System.out.println("b:"+b);       System.out.println("c:"+c);    }  } Output of this program: a:3 b:4 c:5

Program to demonstrate that we can initialize the variables while declaring itself class InitializingVariablesWhileDeclaration {    public static void main(String args[])    {       int a=3,b=4,c=5;    // Initializing the variables by assigning values while declaring the variables itself       System.out.println("a:"+a);       System.out.println("b:"+b);       System.out.println("c:"+c);    }  } Output of this program: a:3 b:4 c:5

Program to demonstrate the dynamic initialization of variables  class DynamicInitialization {    public static void main(String args[])    {       int a=3,b=4;       int c=a+b;    // Initializing the variable c dynamically i.e. while performing a+b operation and assigning it to c       System.out.println("c:"+c);    }  } Output of this program: c:7

Please comment below to feedback or ask questions.

Scope of Variables topic will be explained in the next post.