Lecture-2nd Datatypes and variables in Java

What are Datatypes and Variables in Java ?

Just like we have some rules that we follow to speak english (the grammar) , we have same rules to follow while writing a java code , the set of these rules is called a Syntax 

SYNTAX         : "Vocabulary and Grammar of the Java "

VARIABLE      : "A Variable is a container that stores a value and this value can be changed during                                             execution"

Name of the Variable : You can give any name to you variable , but it will not follow the following Characterstics that is mentioned below:

 1 "MUST NOT START WITH A DIGIT"

            int 12number = 90;   (INVALID)

 2 "NAME IS CASE SENSITIVE"

            int number = 90;   (This is in lower case)

            int NUMBER = 90;  (This is in Upper Case)

 3 "SHOULD NOT BE A KEYWORD"

   

            int Static = 90;    (All the reserve keywords are invalid)

            int public = 89;

 4 "WHITE SPACE NOT ALLOWED"

            int sachin malhotra = 22;   (This is Invalid)

            int sachinmalhotra = 22;    (This is Valid)

 5  "CAN CONTAIN ALPHABETS , $ CHARACTER AND DIGITS IF ABOVE CONDITIONS ARE          MET"

    

            int sachin2__MALHOTRA = 22;  (This is valid)

Datatypes in Java 

Primitive Datatypes : Primitive data types in Java are predefined by the Java language and named as the reserved keywords. A primitive data type does not share a state with other primitive values. Java programming language supports the following eight primitive data types.

Non-Primitive Datatypes : Unlike primitive data types, these are not predefined. These are user-defined data types created by programmers. These data types are used to store multiple values.

Range of the Types of Datatypes

"Byte" =     Takes only 1 byte

"Short" =   Takes only 2 byte

"Integer"= Takes only 4 bytes

"Float"=     Takes only 4 bytes

"Long"=     Takes only 8 bytes

"Double"= Takes only 8 bytes

"Character"= Takes 2 bytes

General Formula of representation of the range of all the datatypes in java

"-(2^8n)/2  to (2^8n)/2"

Quiz Questions:

1 write a java program to add two numbers

2 write a java program to subtract two numbers

3 write a java program to multiply two numbers

4 write a java program to divide two numbers

"Here is code of first program and i hope you will take it as a reference and can solve all the rest of the programs"

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Quiz Code:

package practice1;
// this is my first practice question from java data types
public class Practice1 {

    public static void main(String[] args) {
        // sum of two numbers
        
        int number1 = 2;
        int number2 = 7;
        int sum=number1+number2;
        
        System.out.println("The sum of "+number1+" and "+number2+" are : "+sum);
    }
    
}