Java Basics

 

Java Topics (Unit –I)

1.      Differentiate between C, C++ & Java

2.      Java Introduction (History of Java)

3.      Java Features

4.      Java Applications

5.      Java and Internet

6.      Java and WWW (World Wide Web)

7.      Java Platform (JDK (JVM+JRE) + API)

8.      Structure of Java Program

9.      Java Character set

10.  Java Escape sequences

11.  Java Tokens

12.  Java Datatypes

13.  Java Input and Output statements

14.  Java Statements

15.  Java Sample Programs

16.   

1)    Differentiate between C, C++ & Java

 

	C	C++	JAVA
1. Developed by	Dennis Ritchie	Bjarne Stroustrup	James Gosling
2. Year	1972	1980	1990(Oak), 1995(Renamed java)
3. First Version	1972	1985	JDK Alpha & Beta (1995), JDK1.0-1996
4. Software	Turboc	Turboc++	JDK
5. Lab(Company)	AT&T Bell, USA	AT&T Bell, USA	Sun Micro Systems Adopted Oracle Corp, USA-2010
6. Extension	.c	.cpp	.java
7. Derived from	BCPL	C	C(Syntax) & C++
8. Category             (Paradigms)	Structured Oriented  Language	OOP's(Object Oriented Language)	OOP's(Object Oriented Language)
9. OOP's Concept	Not supported	Supported	Supported
10. Types	Middle level	High level language	High level language
11. Compilation	Compiler	Compiler	Compiler & Interpreter
12.Code Translation	Compiled	Compiled	Interpreted
13. Approach	Top to Bottom	Bottom to Top	Bottom to Top
14. Platform Dependency	Dependent(WOCA) Write Once Compile Anywhere	Dependent(WOCA) Write Once Compile Anywhere	Independent (WORA) Write Once Runs Anywhere
15. Char Format	ASCII	ASCII	Unicode(UTF)
16. Keywords	32	63	53
17. Pointer	Supported	Supported	Not supported
18. Format Specifier	need(%d, %c, %f)	not need	not need
19. goto	Supported	Supported	Not supported
20.Storage Allocation	malloc, calloc	new, delete	garbage collector
21. Header file	Supported	Supported	Not supported (use packages)
22.Constructor	Not  Supported	Supported	Supported
23.Destructor	Not Supported	Supported	Not Supported
24.Operator Overloading	Not Supported	Supported	Not Supported
25.Function Overloading	Not Supported	Supported	Supported
26. inline	Not Supported	Supported	Not Supported
27. this	Not Supported	Supported	Supported
28. Multiple inheritance	Not Supported	Supported	Not Supported
29. virtual	Not Supported	Supported	Not Supported
30. :: (Scope Res olution Operator)	Not Supported	Supported	Not Supported
31. friend keyword	Not Supported	Supported	Not Supported
32. interface	Not Supported	Not Supported	Supported
33. Multithreading	Not Supported	Not Supported	Supported
35. Exception Handling	Not Supported	Supported	Supported
36. Database Connectivity	Not Supported	Not Supported	Supported
37. Networking Programming	Not Supported	Not Supported	Supported
38. Web & Mobile Window(Desktop) Applications	Not Supported	Not Supported	Supported
39. Jagged Array	Not Supported	Not Supported	Supported
40. Constant	const	const	final

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2) Java Introduction (History of Java)

* Java Designed:   James Gosling

* Java Developer :   Sun Microsystems ,USA

* Original Name :   Greentalk After that Oak ,1990’s

* Renamed Java  :   Java,1995’s

* Java Team        :   Green Project

* First Released  :   JDK Alpha & Beta(1995)

* Java Acquired  :   Oracle Corporation (2010)

* Java License    :   GNU General Public License

* Encoding Type :   Unicode character set (UTF-16)

* Java  Browser  :   Hot Java

* Download Type :   Open Source Software(OSS)

* Download & Use :   Free(no cost), Free download & use

* Environment   :   Cross Platform(use Different OS), Machine Independent code(WORA)

* Language Type:   OOP’s (High Level Language)

* Compilation    :   Bottom To Top Approach

* Java Versions  :  JDK Alpha & Beta (1995),  JDK 1.0 (1996), JDK 1.1 (1997), J2SE 1.2 (1998), J2SE 1.3 (2000),J2SE 1.4 (2002),J2SE 5.0 (2004),Java SE 6 (2006),Java SE 7 (2011),

                              …Java SE 15 (2020)... JDK 23.01 (2024)

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3) Java Features

* Simple & Easy to learn

* Case sensitive Language

* Cross Platform & Open Source Software(OSS)

* Object-Oriented Language

* Portable Language

* Platform (Machine) Independent Language (WORA-Write Once Runs Anywhere)

* Secured & Robust, Architecture neutral & Interpreted

* High Performance & Multithreaded Language

* Distributed (Networking) & Dynamic

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4) Java Applications

* Consumer Electronic Devices (Ex: TV, VCD, Mobile)

* Mobile Applications

* Embedded Systems & Cloud based applications

* Web and Web Server Applications

* Desktop or Windows Applications(GUI)

* Business & Enterprise Applications

* Scientific Applications & Big Data Technologies

* 2D & 3D, Virtual Reality Games(VR)

* Editors & Database Applications

* Robotics (Artificial Intelligence(AI))

* Acrobat reader, media player, antivirus, Ultra Mixer, Blu-ray BD-J

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5) Java and Internet

 

Java and Internet

---------------------

·         Java is strongly associated with the Internet because the first application program written in Java was HotJava, a browser to run the applet on Internet. So the Internet users use the Java to create the applet programs and run them locally using a 'Java-enabled browsers' like HotJava

·         -Interconnected Network (a connection of all computers to a central network)

·         -Internet is a network of network

·         -Information Super Highway, to access information over the web

·         -Internet uses the standard Internet Protocol (TCP/IP).

·         -Every computer in internet is identified by a unique IP address.

·         -IP Address is a unique set of numbers (such as 110.22.33.114) which identifies a computer location. A special computer DNS (Domain Name Server) is used to give name to the IP Address. so that user can locate a computer by a name.

       

 

 

 

 

6) Java and WWW

 

·         World Wide Web (WWW), byname the Web, the leading information retrieval service of the Internet (the worldwide computer network).

·         The World Wide Web (WWW) is a network of online content that is formatted in HTML and accessed via HTTP.

·         Java communicates with a Web page through a special tag called <APPLET>.the Figure illustrates the process. It shows the following communication steps:

1)      The user sends a request for an HTML document to the remote computer’s Web server. The Web server is a program that accepts a request, processes the request, and sends the request document.

2)      The HTML document is returned to the user’s browser. The document contains the APPLET tag, which identifies the applet.

3)      The corresponding applet byte code is transferred to the user’s computer. This bytecode had been previously created by the Java compiler using Java source code file for that applet.

4)      The Java enabled browser on the user’s computer interprets the byte codes and provides output.

5)      The user may have further interaction with the applet but with no further downloading from the provider’s Web server. This is because the bytecode contains all the information necessary to interpret the applet.

                   

Web Browser

-----------------

·         web Browser is an application software that allows us to view and explore

·         information on the web.

·         User can request for any web page by just entering a URL into address bar.

·         -Web browser can show text, audio, video, animation and etc.,

 

Browser                   Vendor

-----------                    ----------

1. Internet Explorer - Microsoft

2. Google Chrome - Google

3. Mozilla Firefox - Mozilla

4. Netscape Navigator - Netscape Communications Corp.

5. Opera - Opera Software

6. Safari - Apple

7. Sea Monkey - Mozilla Foundation

8. K-meleon - K-meleon

 

Web Server

-----------------

·         Web server is a computer where the web content is stored.

·         All Information stored on web server

·         Web server that Store, process & deliver (Serves up or Response) Web pages to client

·         The communication between client and server takes place using the Hypertext Transfer Protocol (HTTP).

Ex:

1. Apache - Apache (49%)

2. nginx - NGINX, inc (39%)

3. IIS - Microsoft (9.5%)

4. LiteSpeed – LiteSpeed Technologies(3.4%)

5. GWS - Google(1.0%)

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7) Java Platform (JDK (JVM+JRE) + API)

 

1. JDK (Java Development Kit)

----------

- JDK is a software development Environment.

- It is used for Compile, Debug, Run and developing java applications and applets.

- It includes the Java Runtime Environment (JRE) + Developing Tools

    

List of Tools (Developing Tools)

1. javac  - Java Compiler

2. java    - Java Interpreter

3. jar      - java archiver

4. rmic   - RMI Compiler

5. javah  - Java Header File generator

6. appletviewer – Run applet programs

7. javadoc - documentation generator

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2. JVM (Java Virtual Machine)

----------

- JVM is a virtual machine that enables the execution of Java bytecode

- It Performs Load, Verify, Execute Code and provide Runtime Environment(JRE).

- JVM is Platform Dependent

Source CodeàJava CompileràClass file (byte code)à Java InterpreteràOS

(.java)                     (javac)                         (.class)             (JVM)    ( Linux, Windows)

 

----------------------------------------------------

3. JRE (Java Runtime Environment)

   -----

- The Java Runtime Environment is a set of software tools which are used for developing Java applications.

- It is used to provide the runtime environment.

- It is the implementation of JVM. It physically exists.

- It contains a set of libraries + other files that JVM uses at runtime.

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4. API (Application Programming Interface)

   -----

- API is a Package,

- A java package is a group of similar types of classes, interfaces and sub-packages.

- There are many built-in packages such as java, lang, awt, javax, swing, net, io, util, sql etc.

import package

Ex:

 1) import java.lang.*;

 2) import java.io.*;

 3) import java.util.*;

 4) import java.awt.*;

 5) import java.net.*;

 6) import java.sql.*;

 7) import java.swing.*;

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8) Structure of Java Program

    

Note:

1.      class: class keyword is used to declare a class in java.

2.      public: public keyword is an access modifier which represents visibility. It means it is visible to all.

3.      void: void is the return type of the method. It means it doesn't return any value.

4.      static: static is a keyword. If we declare any method as static, it is known as the static method. The core advantage of the static method is that there is no need to create an object to invoke the static method. The main method is executed by the JVM, so it doesn't require to create an object to invoke the main method. So it saves memory.

5.      main(): Java program processing starts with the method main(). Each java program must have only one main() method.

6.      String[] args is used for command line argument.

 

//Example Program for java

class first{ 

   public static void main(String args[]){  

     System.out.println(“Welcome to java”);

}

}

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9) Java Character Set

—  In Java, A character set defines the valid characters that can be used in source programs or interpreted when a program is running.

 

1. Alphabets   : All capital (A-Z) and small (a-z) alphabets.

2. Digits          : All digits 0-9.

3. Special Symbols: Java supports all kind of special symbols like, ” ‘ l ; : ! ~ @ # $ % ^ ` & * ( ) _ + – = { } [ ] \ .

4. White Spaces: White spaces like tab space, blank space, newline, and carriage return.

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10) Java Escape Sequences

    -Escape Sequences(characters) is used to perform some specific task

1. \t - insert a tab.

2. \’ - insert a single quote.

3. \" - insert a double quote.

4. \r - insert a carriage return.

5. \\ - insert a backslash character.

6. \n - insert a new line.

7. \f - insert a form feed.

8. \b - insert a backspace.

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11) Java Tokens

- The smallest element (Individual units) of the Java program is called tokens.

 

There are six types of Tokens

------------------------------------

1. Identifier

2. Keywords

3. Constant(Literals)

4. Operators

5. Separators

6. Comment

 

1. Identifier:

---------------

- Identifiers are the names given to the fundamental building blocks in a program.

- Identifier can be a name of the variables, class, object, functions, arrays

 

     

 

 

 

Variable

-----------

·         Variable is used to store a value during a runtime

·         Variable also known as identifier. Variable is a name of memory location (Reserved Area).

·         Variables are case sensitive (A and a both are two different variables).

 

Declare a java variable:

Syntax:

           datatype variable = value;

Example:

  int a=10;

  float b=13.5;

  String name="jahab";

 

 

There are three types of variables in java:

    1) local variable: inside the body

    2) instance variable: inside the class

    3) static variable: use static keyword

 

 

Rules for naming a variable

------------------------------------

—  A variable name can only have letters (both uppercase (A to Z) and lowercase (a to z)), digits (0 to 9), $(dollar) and underscore.

—  Don’t start with digits but end or mix with digits(numbers)

—  spaces or special characters (+, -, *, /, %) are not allowed.

—  Names are case sensitive (“name" and “Name" are different variables)

—  Reserved words (like Java keywords, such as int or float) cannot be used as names

Ex:

 Studentname   - valid

 Student name  - invalid (space)

 Student_name - valid

 10student        - invalid (start with digits)

 Student10       - valid

 

//Example program for variable

class test{

    public static void main (String args[]) {

        int a=10;

        float pi=3.14f;

        char ch='a';

        String name="Jahab";

       System.out.println(a);

       System.out.println(pi);

       System.out.println(ch);

       System.out.println(name);

    }

}

---------------------------------------

 

 

2. Keywords:

   -------------

- Keywords are the pre-defined reserved words of java programming.

- Each keyword has a special meaning. It is always written in lower case.

 

List of Keywords

------------------------------------------------

 

3.  Java Constant (Literals)

     -------------------

- Constant Refer to fixed values. The Value of Quantity which does not vary or alter throughout the program. These fixed values are also called Literals

 

Types of Literals (Constant)

//Example program for constant

class test{

    public static void main (String args[]) {

         final int a=10;

        final float pi=3.14f;

        final char ch='a';

        final String name="Jahab";

        System.out.println(a);

        System.out.println(pi);

        System.out.println(ch);

        System.out.println(name);

} }

-----------------------------------------------

4. Java Operators

-----------------------

·         Operator in Java is a symbol that is used to perform operations. For example: +, -, *, / etc.

 

Types of Operators

----------------------

1. Arithmetic Operator            :           +, -, *, /, %

2. Relational Operator            :           >,>=, <, <=, ==, !=

3. Logical operator                  :           &&, ||, !

4. Increment (++) or decrement (--) operator or Unary Operator (-): ++,--, -

5. Assignment Operator             : =, +=, -=, *=, /=, %=

6. Ternary Operator or conditional operator: ( ?: )

7. Bitwise Operators   :           &, |, ^, ~, <<, >>, >>>

--------------------------

//Example program for Arithmetic operators: +, -, *, /, %

class test{

    public static void main (String args[]) {

        int a = 10, b = 30;

        // Arithmetic operators

        System.out.println("a + b = " + (a + b));

        System.out.println("a - b = " + (a - b));

        System.out.println("a * b = " + (a * b));

        System.out.println("a / b = " + (a / b));

        System.out.println("a % b = " + (a % b));

       }

}

--------

//Example program for Relational operators: >,>=, <, <=, ==, !=

class test{

    public static void main (String args[]) {

        int num1 = 10, num2 = 30;

    // Relational operators

    System.out.println("num1 > num2 is " + (num1 > num2));

    System.out.println("num1 < num2 is " + (num1 < num2));

    System.out.println("num1 >= num2 is " + (num1 >= num2));

    System.out.println("num1 <= num2 is " + (num1 <= num2));

    System.out.println("num1 == num2 is " + (num1 == num2));

    System.out.println("num1 != num2 is " + (num1 != num2));

       }

}

---------

//Example program for Logical operators: &&, ||, !

class test{

    public static void main (String args[]) {

        int x = 10, y = 30, z = 5;

    // Logical operators

        System.out.println(x > y && x > z);

        System.out.println(x > y || x > z);

        System.out.println(!(x > y || x > z));   

      }

}

----------------

//Example program for Increment & Decrement (Unary Operator): ++, --, -

class test{

    public static void main (String args[]) {

       int x = 5;

       System.out.println(++x);

       System.out.println(x++);

       System.out.println(--x);

       System.out.println(x--);

       System.out.println(-x);

  }

}

------------------

 

//Example program for Assignment operators: =, +=, -=, *=, /=, %=

class test{

    public static void main (String args[]) {

    int x = 5;

    x += 3;

    System.out.println(x);

    x -= 3;

    System.out.println(x);

    x /= 3;

    System.out.println(x);

    x *= 3;

    System.out.println(x);

    x %= 3;

    System.out.println(x);

    int a=b=c=10;    //Multiple Assignment

    }

}

-----------------

//Example program for Ternary or Conditional operators:  ?:

class test{

    public static void main (String args[]) {

    int a=5,b=10;

    int max = (a>b) ? a : b ;

    System.out.println(max);

  }

}

----------------

//Example program for Bitwise operators: &, |, ^, ~, <<, >>, >>>

class test{

    public static void main (String args[]) {

    int x = 10, y = 8;

    System.out.println(x&y);

    System.out.println(x|y);

    System.out.println(x^y);

    System.out.println(~x);

  } }

---------------------------------------------------------------------------

5. Java Separators

 -----------------------

—  The separators in Java is also known as punctuators. Separators help define the structure of a program.

 

          

--------------------------------------------------------------------------------------------

 

6. Java Comments

------------------------

—  Java Comments used to specify information about the program inside our Java code. The Java compiler treats comments as whitespaces.

 

                            

 

Types of Java Comments:

1. Single Line comment: 

·         It begins with a pair of forwarding slashes (//).

·         It is used to refer program title, Author name and single line description

    Ex:  //Program 1: display your name

 

2. Multi-line Comment (block):

·         It begins with /* and continues until it founds */.

·         It is used to program description (paragraph format)

    Ex:   /*

              The code below will print the words Hello to the screen

              The code below will print the words Hello to the screen

              The code below will print the words Hello to the screen

              The code below will print the words Hello to the screen

           */

----------------------------

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

 

 

12) Java Datatypes

·         Data types specify the different sizes and values that can be stored in the variable.

There are two types of data types in Java:

1. Primitive data types: The primitive data types include boolean, char, byte, short, int, long, float and double.
2. Non-primitive data types: The non-primitive data types include Classes, Interfaces, and Arrays.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

13) Java Input and Output Statements

 

Input Statement:

—  Input (getting data from user through keyboard) is any information that is needed by your program to complete its execution. (Read input from console)

 

     

Scanner class:

—  The Scanner class is used to get user input, and it is found in the java.util package.

—  Scanner class is a simple text scanner which can parse primitive types (like int, float, double) and strings

1) Import Scanner class:

import java.util.Scanner;

2) Create a Scanner Object in Java

            Scanner obj = new Scanner(System.in);  

 

List of Scanner Class Methods

Method	Description
nextBoolean()	Reads a boolean value from the user
nextByte()	Reads a byte value from the user
nextDouble()	Reads a double value from the user
nextFloat()	Reads a float value from the user
nextInt()	Reads a int value from the user
nextLine()	Reads a String value from the user
nextLong()	Reads a long value from the user
nextShort()	Reads a short value from the user

 

//Example program from Scanner class

import java.util.Scanner;

class test {

  public static void main(String[] args) {

    Scanner obj = new Scanner(System.in);

    System.out.print("Enter name: ");

    String name = obj.nextLine();   //String input

    System.out.print("Enter Age: ");

    int age = obj.nextInt();           // Integer

    System.out.print("Enter Salary: ");

    double salary = obj.nextDouble();  //Floating point

    // Output input by user

    System.out.println("Name: " + name);

    System.out.println("Age: " + age);

    System.out.println("Salary: " + salary);

  }

}

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14) Java Statements

 

·         In Java, a statement is an executable instruction that tells the compiler what to perform. It forms a complete command to be executed and can include one or more expressions.

Types of Statements

1. Expression Statements
2. Declaration Statements
3. Control Statements

 

1.      Expression Statements

·         Expression is an essential building block of any Java program.

·        In Java, expression is the combination of values, variables, operators, and method calls.

Ex:

  Assign values

        int a = 10;       

        float pi=3.14f;

        char ch='a';

        String name="Jahab";

  Expression

            c = a + b;

            v = 1/3 * 3.14 * r * r * h;

            b = (6 + 9);

------------------------------------------------

2.      Declaration Statements

·         In declaration statements, we declare variables and constants by specifying their data type and name. A variable holds a value that is going to use in the Java program.

For example:

        int a,b,c;

        float pi;

        char ch;

        String name;

---------------------------------------------------

3.      Control Statements

·         Control statements decide the flow (order or sequence of execution of statements) of a Java program. In Java, statements are parsed from top to bottom.

·         Therefore, using the control flow statements can interrupt a particular section of a program based on a certain condition.

 

-------------------------------------------

Example of Statement

//declaration statement  

int number;  

//expression statement  

number = 412;  

//control flow statement  

if (number > 100) {  

     System.out.println(number + " is greater than 100");  

}  

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

15) Java Example Programs

 

//Program 1: Addition of two numbers(Integer)

import java.util.Scanner;

class test {

  public static void main(String[] args) {

    Scanner dis = new Scanner(System.in);

    System.out.print("Enter First value :");

    int a = dis.nextInt();

    System.out.print("Enter Second value :");

    int b = dis.nextInt();

    int add = a + b;

    System.out.println("Addition is :"+add);

  }

}

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

//Program 2: Addition of two numbers(Float)

import java.util.Scanner;

class test {

  public static void main(String[] args) {

    Scanner dis = new Scanner(System.in);

    System.out.print("Enter First value :");

    float a = dis.nextFloat();

    System.out.print("Enter Second value :");

    float b = dis.nextFloat();

    float add = a + b;

    System.out.println("Addition is :"+add);

  }

}

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

//Program 3: Simple Interest calculations

import java.util.Scanner;

class test {

  public static void main(String[] args) {

    Scanner dis = new Scanner(System.in);

    System.out.print("Enter Principle Amount :");

    float p = dis.nextFloat();

    System.out.print("Enter No of years :");

    float n = dis.nextFloat();

    System.out.print("Enter Rate of interest :");

    float r = dis.nextFloat();

    float si = p * n * r / 100;

    System.out.println("Simple Interest is :"+si);

  }

}

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

//Program 4: Volume of cone

import java.util.Scanner;

class test {

  public static void main(String[] args) {

    Scanner dis = new Scanner(System.in);

    System.out.print("Enter Radious value :");

    float r = dis.nextFloat();

    System.out.print("Enter Height value :");

    float h = dis.nextFloat();

    double v = (1.0/3.0) * Math.PI * Math.pow(r,2) * h;

    System.out.println("Volume of Cone is :"+v);

    System.out.printf("Volume of Cone is : %.2f",v);

  }

}

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