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Basic Java – 2 || Variables and Data Types used in JAVA.

            As the name sounds “Vary+able”, means the value can be changed. Basically, the variable is the name of the memory location which is used to store and retrieve the value in it.

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Definition and Types of Variable

          Variables are reserved memories to store values in RAM. These memories get released as soon as the life of variable gets finished. Based on the life of variables there are three types of Variable.
1. Local Variables: Life remains within a block where it has been declared.
2. Instance Variables: Declared inside the Class but outside the methods. It shouldn’t be static.
3. Static Variables: It’s like a Global variable. Declared as static in the class but outside the methods.

public class Variables {
       int instanceVar=5;
       static int staticVar=8;

       public static void main(String[] args) 
       {
               int localVar=10;
               System.out.println("Loacal Variable:"+localVar);
               localVar+=50;
      Variables obj=new Variables();
      System.out.println("Instance Variable: "+obj.instanceVar);
      obj.instanceVar+=50;      
               System.out.println("Static Variable: "+staticVar);
       }
}

         In the above example, the life of localVar will be within the main() method only. If we try to use the same variable outside the main method it will throw an error.

instanceVar can be accessed only through objects of the ‘Variables’ class.

staticVar can be used without any object and can be used only in the static methods.

Variables Naming Convention

The variable name should start with letters, $ and _. We can’t use any other character as well as java reserved keywords.
Valid example:
myVar
myVar1
$myvar
_myvar

Invalid example:
1myvar
*myvar
void (Java reserved Keyword)
int (Java reserved Keyword)
static (Java reserved Keyword)

Data Types in JAVA

             Simply data types tell the compiler type of variable. It tells the compiler which type of data a variable can store in it. For example, an integer variable can store only numeric values. If we try to store a letter in that variable, the compiler will throw an error.
Basically, there are two types of Data Type:
1. Primitive: Known as primary data types. These data types are not breakable further. These are self-explanatory like boolean, short, int, long, float, char, double, byte.
2. Non-Primitive(Reference): Data type which has been created using the Primitive data types like String, Array, Enum etc.

Escape Sequence

           Java language supports few special escape sequences for String and char literals as well.
The escape sequence is a character which can change the meaning of other characters which follow it.
Most used escape sequence:
\n        Newline (0x0a)
\”        Double quote
\’        Single quote
\\        backslash

Example:

Suppose we have to print the following sentence:

Nancy said “Hello World” to the crowd.

print “Nancy said “Hello World!” to the crowd.”;
produces a syntax error, whereas:

print “Nancy said \”Hello World!\” to the crowd.”;  ### example of \”
produces the intended output:

Variable Declaration and Initialization

The declaration is to define a variable and its type, for example:

int rollNumber;

Initialization is to assigning correct value to a variable:

rollNumber=10;

We can combine both the above steps as mentioned below:

int rollNumber=10;

String name=”testData”;  // To store any string value we have to mention it within the quotes.

float myVar=4.5;              // To store float values

boolean flag=true;           // true and false are java reserved keywords.

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            Ashok Kumar is working in an IT Company as a QA Consultant. He has started his career as a Test Trainee in manual testing in August 2010. Then he moves towards the automation testing after 4 years. He started learning JAVA and Selenium by self to get the knowledge of automation.

       While learning these tools and working on multiple projects, he found that sometimes people get stuck in live scenarios in their project and they have to do lots of RnD to get out of it. So he decided to start blogging only for such scenarios, where anyone facing any problem in their project, can ask any question or give a solution or you can say an alternate solution to achieve the goal successfully.

Later on, he observed that some people want to learn Java but they have few questions in their mind like how to start Java, whether we should go for the online or offline course. So he started writing tutorials on Java, Jira, Selenium, Excel etc.