JAVA TUTORIAL

JAVA DEFINTION:

* Java is a popular programming language,Created in 1995.

*It is owend by Oracle,and more than 3billion device run in java.

*Java is used to develop  mobile  application, web  application, Desktop application, Games and so on.

SYNTAX:

public class NAME
{
public static void main (String args[])
{
System.out.println(" ");
}

1.public class NAME
  • Public --> Access modifier. It means the class can be accessed from anywhere in the program.
  • Class --> Keyword used to create a class in java.
  • name -->Class name. You can replace NAME with any vaild class name such as Hello, Student, etc..
2.public static void main (String args[])

This is the main method, where Java strats executing the program.

Public:
  • The method can be accessed by the JVM (Java Virtual Machine).
Static
  • Allows the method to be called without creating an object of the class.
void
  • The method does not return any value.
main
  • Specail method name recognized by the JVM as the entry point of the program
String args[]
  • Stores command-line arguments passed when running the program.
  • args is an array of string objects.

3. System.out.println(" ");

Used to print otput on the console

System
  • A built_in java class
out
  • Standard output steam (console).
println(" ");
  • Prints the text and moves the cursor to the next line.

sample program:

we created file name sample.java.

public class sample
{
public static void main (String args[])
{
System.out.println("hello world!")

System.out.println("I am hero")

System.out.println("my favourite food Biriyani")

}

}

output:

hello world!

I am hero

my favourite food Biriyani



JAVA COMMENTS:

Java is used to the two types of comments ( // ) and (/* ------- */).

1. // I am learning java.

2./* Java is a popular programming language .It is Awesome! */.


Difference between JDK, JRE, and JVM :


Variable are containars for storing data values.

TYPES OF VARIABLE:

1.String - store text in double quotes "HELLO".

2.int -store integers (whole number),such as 123 or -123.

3.float-store floating point numbers,with decimal ,such as 19.99 0r -19.99.

4.char-strings are store single characters 'a' or 'z'.

5.boolean-store values in two states:True or False.

program:

public class variable {
public static void main(String[] args) {

String name = "John";     // String variable
int myNum = 5;            // Integer variable
float myFloatNum = 5.99f; // Float variable
char myLetter = 'D';      // Character variable
boolean myBool = true;    // Boolean variable

// Printing all variables

System.out.println(name);
System.out.println(myNum);
System.out.println(myFloatNum);
System.out.println(myLetter);
System.out.println(myBool);

}

}
output:

John
5
5.99
D
true



JAVA DATETYPES:

Java datatypes is two types primitive and non-primitive.

Primitive:

  • These are the basic built-in type provide in java.
  • They store simple value directly in memory.
  • Primitive datatypes such as byte, short, int, long, float, double, boolean and char.

Non-Primitive:

  • These are created by the programmer are java libraries that can store collection of data and complex structure..
  • Also known as reference types.
  • Non-Primitive datatypes such as String, Arrays and classes.

program:

public class datatypes {
public static void main(String[] args) {

int mynum = 1000;    // 4 bytes, range: -2,147,483,648 to 2,147,483,647
byte mybyte = 100;     // 1 byte, range: -128 to 127
short myshort = 10000;    // 2 bytes, range: -32,768 to 32,767
long mylong = 5000001L;   // 8 bytes, range: -9 quintillion to +9 quintillion
float myfloat = 7.6f;            // 4 bytes, ~6 to 7 decimal digits precision
double mydouble = 733.88888888d; // 8 bytes, ~15 decimal digits precision

System.out.println(mynum);
System.out.println(mybyte);
System.out.println(myshort);
System.out.println(mylong);
System.out.println(myfloat);
System.out.println(mydouble);
}
}
output:

1000
100
10000
5000001
7.6
733.88888888888



Java Type Casting:
Type casting means converting one data types into another. For example, turning an int into double.

In Java, ther eare two types of casting:
  • Widening Casting ( Automatic ) --> Converting a smallar type to larger type size.

    byte -> short -> char -> int -> long -> float -> double
  • Narrowing Casting ( manual ) ---> Converting a larger type to smaller type size.

    double -> float -> long -> int -> char -> short -> byte

Java operators:

1.Arithmetic Operators:

Arithmetic operators are used to perform common mathematical operations.

Operator Name Description Example
+ Addition Adds two values together x + y
- Subtraction Subtracts one value from another x - y
* Multiplication Multiplies two values x * y
/ Division Divides one value by another x / y
% Modulus Returns the division remainder x % y
++ Increment Increases the value of a variable by 1 ++x
-- Decrement Decreases the value of a variable by 1 --x

program:

public class arithmeticoperators {

    public static void main(String[] args) {
        int x = 10;
        int y = 3;
        int z = 8;

        System.out.println(x + y); // add 13
        System.out.println(x - y); // sub 7
        System.out.println(x * y); // multi 30
        System.out.println(x / y); // div 3
        System.out.println(x % y); // mod 1

        ++z;
        System.out.println(z); // inc 9
        --z;
        System.out.println(z); // dec 8
    }
}

output:

PS C:\Manijava> javac arithmeticoperators.java PS C:\Manijava> java arithmeticoperators.java 13 7 30 3 1 9 8


2.Assignment Operators:

Assignment operators are used to assign values to variables.

The reason is that assignment operators change the value of the variable itself. After each statement, X gets a new value.

Operator Example Same As Description
= x = 5 x = 5 Assign value to variable
+= x += 3 x = x + 3 Add and assign
-= x -= 3 x = x - 3 Subtract and assign
*= x *= 3 x = x * 3 Multiply and assign
/= x /= 3 x = x / 3 Divide and assign
%= x %= 3 x = x % 3 Modulus and assign
&= x &= 3 x = x & 3 Bitwise AND and assign
|= x |= 3 x = x | 3 Bitwise OR and assign
^= x ^= 3 x = x ^ 3 Bitwise XOR and assign
>>= x >>= 3 x = x >> 3 Right Shift and assign
<<= x <<= 3 x = x << 3 Left Shift and assign
>>>= x >>>= 3 x = x >>> 3 Unsigned Right Shift and assign

Program:

public class assignment {
    public static void main(String[] args) {

        int x = 10;

        System.out.println("Initial value: " + x);

        x += 5; // x = x + 5
        System.out.println("x += 5 : " + x);

        x -= 3; // x = x - 3
        System.out.println("x -= 3 : " + x);

        x *= 2; // x = x * 2
        System.out.println("x *= 2 : " + x);

        x /= 4; // x = x / 4
        System.out.println("x /= 4 : " + x);

        x %= 3; // x = x % 3
        System.out.println("x %= 3 : " + x);
    }
}

Output:

PS C:\Manijava> javac assignment.java PS C:\Manijava> java assignment.java Initial value: 10 x += 5 : 15 x -= 3 : 12 x *= 2 : 24 x /= 4 : 6 x %= 3 : 0

JAVA OOPS CONCEPT:

Java oops(object-orient programming system) concepts are the core ideas of java programming based on real-world objects.

They  helps in organizing code,making it reusable, modular, and easier to maintain.

The four main OOP concept in java:-

  1. Encapsulation.
  2. Inheritance.
  3. Polymorphism.
  4. Abstraction.

class/object:

A class is a blueprint for creating object.
It contains Variable(attributes) and methods (behaviours).

An object are instance of a class.
Object are created using the new keywords.


Program:

public class Laptop{
    String name="";
    String proc="";
    int ram=0;
    int price=0;
    public static void main(String[] args)
    {
    Laptop lap1 = new Laptop();
    Laptop lap2 = new Laptop();

        lap1.name="HP";
        lap1.proc="i5";
        lap1.ram=4;
        lap1.price=50000;

        lap2.name="Lenova";
        lap2.proc="i7";
        lap2.ram=6;
        lap2.price=80000;
System.out.println("lap1:"+lap1.price);
       System.out.println("lap2:"+lap2.price);
    }  
    }

output:
lap1:50000 lap2:80000



2.ENCAPSULATION:
  • Declare class attribute/variable as Private.
  • Provide public getter and setter methods to access and update the value of a Private variable.

Program:

class ClassA{
    private String name;   //private data
    private int age;

    //getter
    public String getName(){
        return name;
    }
   
    //setter
    public void setName(String name){
        this.name = name;
    }

    public int getAge(){
        return age;
    }
    public void setAge(int age){
        if (age >0){
            this.age = age;
        }
    }
}

public class Student{
    public static void main(String[] args) {
        ClassA c =new ClassA();
        c.setName("Mani");
        c.setAge(20);

        System.out.println("Name:" + c.getName());
         System.out.println("Age:" + c.getAge());
    }
   
}

output:

PS C:\Manijava> javac Student.java PS C:\Manijava> java Student.java Name:Mani Age:20 PS C:\Manijava>



INHERITANCE:

  • One class inherits the prorperties and methods of another class using extends -->key. 
  • Promote reusabilty

Five main type of inheritance:

  1. Single Inheritance.
  2. Multilevel inheritance.
  3. Hierarchical Inheritance.
  4. Multiple Inheritance.(not directly supported in java with classes)
  5. Hybrid Inheritance.

1.Single Inheritance.

---->One class inherits another.

program:

class Animal{
    void eat() {
        System.out.println("Eating...");
        }
}

class Dog extends Animal{
    void bark(){
        System.out.println("Barking...");
    }
}

public class single {
    public static void main(String[] args){
        Dog d = new Dog();
        d.eat(); //from parent
        d.bark(); //from child
    }

}


output:

PS C:\Manijava> javac single.java PS C:\Manijava> java single.java Eating... Barking...



2.Multilevel Inheritance.

---->A class inherits from another class, which again inherits from another. 

program:

class Grandparent {
    void house() {
        System.out.println("Grandparent has a house");
    }
}
class Parent extends Grandparent {
    void car() {
        System.out.println("Parent has a car");
    }
}
class Child extends Parent {
    void bike() {
        System.out.println("Child has a bike");
    }
}
public class multilevel {
    public static void main(String[] args) {
        Child c = new Child();
        c.house(); // from Grandparent
        c.car();   // from Parent
        c.bike();  // from Child
    }
}

Output:

PS C:\Manijava> javac multilevel.java PS C:\Manijava> java multilevel Grandparent has a house Parent has a car Child has a bike PS C:\Manijava>




3.Hierarchical Inheritance.

---->Multiple classes inherit from a single parent.


4.Multiple Inheritance.(not directly supported in java with classes)

---->Java does not allow multiple inhertance using classes.

---->But java supports multiple inhertance using interfaces.

5.Hybrid Inheritance.

---->Java does not support hybrid inheritance with classes,but we can achieve it using interfaces.

POLYMORPHISM:

  • Polymorphism means "many forms".

Two types of Polymorphism:

1.Complie-time(method overloading).

2.Run-time(method overriding).

1.Complie-time(method overloading).

Same method name , but different parameter lists.

Decided by complietime Polymorphism(early binding).

program:

class mathoperation {
    int add(int a, int b) {
        return a + b;
    }
    double add(double a, double b) {
        return a + b;
    }
}

public class operation {
    public static void main(String[] args) {
        mathoperation m = new mathoperation();
        System.out.println(m.add(2, 3));       // int version → 5
        System.out.println(m.add(2.5, 3.5));   // double version → 6.0
    }
}

output:

PS C:\Manijava> javac operation.java

PS C:\Manijava> java operation

5

6.0


2.Run-time(method overriding).

  • Child class provides a new implemention of a parent method.
  • Decided at runtime Polymorphism(late binding).

Program:

class Animal {
    void sound() {
        System.out.println("Animal makes sound");
    }
}

class Dog extends Animal {
    void sound() {
        System.out.println("Dog barks");
    }
}

public class overriding {
    public static void main(String[] args) {
        Animal a = new Dog();  // parent reference, child object
        a.sound();             // calls Dog’s sound()
    }

}

output:

PS C:\Manijava> javac overriding.java PS C:\Manijava> java overriding Dog barks


ABSTRACTION:
  • Hinding implementation details and showing only essitential feature.
  • Achived using abstract class or interface.
  • Abstract class cannot create object directly.
  • Abstract method has no body,must be implemented by child.
program:

abstract class vehicle{
    abstract void speed();
}
class Bike extends vehicle{
    void speed()
    {
        System.out.println("50km.hr");
    }
    }
class car extends vehicle{
        @Override
        void speed() {
        System.out.println("100km.hr");
    }
    }
public class abs {
    public static void main(String[] args) {
        vehicle v1 = new Bike();
        vehicle v2 = new car();
        v1.speed();
        v2.speed();
    }
    }
output:
PS C:\Manijava> javac abs.java PS C:\Manijava> java abs 50km.hr 100km.hr



Error in java:
java error commonly grouped into 3 categories
  1. Syntax error (Compile-time error). ---> You assembled the bike incorrectly
  2. Run-time error. ---> The bike breaks while riding.
  3. Logical error. ---> The bike works, but you go to the wrong destination.
1.Syntax error (Compile-time error).
    Mistakes in java grammar or syntax.
    For example: forgot the Semicolon (;) , Mismatch types and Undeclared variable. 

example:
public class Test {
    public static void main(String[] args) {
        System.out.println("Hello World")
    }
}
 
ERROR:
       ' ; ' expected.

2.Runtime error:
       The code complies successfully , but crashes while running.
        For example:
example:


Comments

Post a Comment

Popular posts from this blog

ORACLE DBA

Image
DAY:1 Database in collect the information in note pad ,txt ,excl etc..  Database is stored in RAM,CPU etc.. Database is collect the date for names, salaries, information, pictures, videos and anything store in database. A Database is, basically , a place that we store an organized collection of data. store, access, manipulate, retrieve. DBMS: This DBMS type is hierarchical, network, relational, object-relational DBMS. ORACLE DATABASE: Oracle database is very secured, performance, scalability,powerful coding and support a company. DAY:2 Table is used employee date store the union of all these horizontal cell is called as a record or a row. The table stored the data such that employees ID, Name, salary, phone number, department etc.. Tabular form like in job interviews or exams,etc..  RELATION DATABASE: If you create two table employees and department table. To  the employees related  the department table its relational data base. Relational databas...
Read more

JSP TUTORIAL

Image
INTRODUCTION OF JSP: 1.What is jsp. 2.How jsp works in Servlet. 3.JSP VS Servlet. 4.JSP life Cycle. What is jsp: JSP ( Java Server Page) is a server side technology used to create dynamic , paltform-indepentent web application using java. When jsp page requested by User, it is complied into a servlet by the server and the server handle the request. How jsp Works (behind the scenes): A (.jsp) file is requested by a user.. The JSP Engine on the server converts it into the Servlet.   The servlet is complied and executed. The Response (HTML) is send back to the browser. JSP VS Servlet: JSP life Cycle: LINK : https://data-flair.training/blogs/jsp-life-cycle/ DIFFERENCE BETWEEN A WEBSERVER ,WEB CONTAINER AND AN APPLICATION SERVER: WEB SERVER:   It is receives  HTTP request , intercepts it. It also processes the HTTP response to the web browser of the client. EX: Apache Web server. WEB CONTAINER : A web container is J2EE compliant implementation.Its mains the job is run the ru...
Read more