variables in java

 Today we will explain primitive data types , arithmetic operators and variables in java 

 Data types : 

byte, short, int and long data types are used for storing whole numbers.

float and double are used for fractional numbers.

char and string which are used for storing characters(letters).

boolean data type is used for variables that holds either true or false

 

 

 

 

variables :

     variable is a name of reserved area in the computer's memory or it's a name of memory location , an d we have three main types of variables in java 

• local variables : which are defined inside some method's body
• instance variables : which are defined out side method body , but in side class body 
• static variables : which are defined by using "static" word before we defined them , and they can not be defined inside method body

Now :  we can define any variable as bellow 

 

data_type variable_name = value;

 

 

arithmetic operators : 

  

 

 

Now let us go to our example today , and we will explain the code which it's output just as in the image bellow 

 

 

 and the code will be just as 

public class test{
    public static void main(String[]args){
        int num = 10;
        System.out.println("________________________");
        System.out.println();
        System.out.println("      "+num+" * 1 "+" = "+num*1);
        System.out.println("      "+num+" * 2 "+" = "+num*2);
        System.out.println("      "+num+" * 3 "+" = "+num*3);
        System.out.println("      "+num+" * 4 "+" = "+num*4);
        System.out.println("      "+num+" * 5 "+" = "+num*5);
        System.out.println("      "+num+" * 6 "+" = "+num*6);
        System.out.println("      "+num+" * 7 "+" = "+num*7);
        System.out.println("      "+num+" * 8 "+" = "+num*8);
        System.out.println("      "+num+" * 9 "+" = "+num*9);
        System.out.println("      "+num+" * 10 "+" = "+num*10);
        System.out.println("      "+num+" * 11 "+" = "+num*11);
        System.out.println("      "+num+" * 12 "+" = "+num*12);
        System.out.println();
        System.out.println("_________________________");
        System.out.println();
        System.out.println();
        System.out.println();
    }
}

 

Home Work ?

write a java code that give the output in the image bellow 

 

 

 

 

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java's principles

java

Today we will start coding java , but first we must explain some important thing and principles 

 

Package : is a mechanism to encapsulate a group of classes, sub packages and interfaces and package can be used for 

• Preventing naming conflicts
• Making searching/locating and usage of classes, interfaces, enumerations and annotations easier
• Providing controlled acces

packages in java has two main types :

• Built-in Packages : These packages consist of a large number of classes which are a part of Java API ( java.lang ,  java.io ,  java.util)
• User-defined packages : These are the packages that are defined by the user

Class : is a user defined blueprint or prototype from which objects are created , has (Modifiers , Class name , Superclass , Interfaces, Body )

Method : is a collection of statements that are grouped together to perform an operation

 

 Compiler : is a program that takes the text file work of a developer and compiles it into a platform-independent Java file. Java compilers include the Java Programming Language Compiler (javac), the GNU Compiler for Java (GCJ), the Eclipse Compiler for Java (ECJ) and  Jikes.

 

Error in programming : 

• Syntax errors : These are errors where the compiler finds something wrong with your program, and you can't even try to execute it
• Runtime errors : Java may detect an error while your program is running 
• Logic errors : logic error, or bug, is when your program compiles and runs, but does the wrong thing. The Java system, of course, has no idea what your program is supposed to do, so it provides no additional information to help you find the error 

Now we can go to write our first java program which has the output just like in the image bellow  

 

___________________________________________

 

this is the code , and we explain it on the video bellow 

 

public class test{
    public static void main(String[]args){
        System.out.println("____________________________________________________________________");
        System.out.println();
        System.out.println("                         Wellcome To Java");
        System.out.println();
        System.out.println("____________________________________________________________________");
        System.out.println();
        System.out.println();
        System.out.println();
        System.out.println();
    }
}

 

watch on YouTube

 

 

 

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