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Configuration for PWC-4
BCSE103E: Computer Programming: JAVA
Module 1: JAVA Basics
Dr. K. Anandavel
Anandavel.k@vit.ac.in
Mob: 770 880 4923
Room: 313-A43, SJT
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Contents
 History of JAVA
 Features of JAVA
 JAVA
 Programming cycle
 Byte code
 Applications
 Programming structure
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History of JAVA
 James Gosling and Patrick Naughton initiated the Java
language project in June 1991.
 The idea was to develop a language which was
platform-independent
and
which
could
create
embedded software for consumer electronic devices,
 It took 18 months to develop and had an initial name
as Oak, Renamed to Java in 1995, due to copyright
issues.
 Java originally developed by James Gosling at Sun
Microsystems and released in 1995
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History of JAVA
Versions
• 1995 version 1.0:
– The Java development kit was released for free by the Sun
– 8-Packages
212-Classes
– Microsoft and other companies licensed Java
• 1997 version 1.1:
– 23 -Packages 504-Classes
– Improvement include better event handling inner classes ,
improved JVM.
– Microsoft developed its own 1.1 compatible Java Virtual
Machine for Internet Explorer
– Many browsers in use are still compatible only with 1.1
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History of JAVA
Versions
1999 version 1.2:
-It is also called as the Java 2 platform
-59 Packages
-1520 Classes
-Code & tools distributed as the SDK
-A Java foundation class based on swings for improved graphics
and user interfaces
-Collection API included list sets and hash map
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History of JAVA
Versions
. 2000 VERSION 1.3:
- 76 Packages
- 1842 Classes
- Java Sound (API for Digital & MIDI Sound)
•2002 VERSION 1.4:
- 135 Packages - 2991 Classes
- Improved XML support etc..,
•2004 VERSION 5.0 (1.5):
- 165 Packages - over 3000 Classes
- Faster startup metadata formatted Output
- Generic to operate on objects of various types
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History of JAVA
Versions
2006 Java SE 6:
– Scripting language support
2011 Java SE 7:
– JVM Support for dynamic language
– String in switch
– Allowing underscores in numeric literals
2014 Java SE 8:
– for Each() method in Iterable interface.
- default and static methods in Interfaces.
- Functional Interfaces and Lambda Expressions.
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History of JAVA
Versions
2017 Java SE 9:
-Stream API Improvements
-Multi-Resolution Image API
Java SE 10 (20th Mar 2018)
Java SE 11 (September 2018)
Java SE 12 (March 2019)
Java SE 13 (September 2019)
Java SE 14 (Mar 2020)
Java SE 15 (September 2020)
Java SE 16 (Mar 2021)
Java SE 17 (September 2021)
Java SE 18 (March 2022)
Java SE 19 (Sep 2022)
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Features of JAVA
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Features of JAVA
Simple
 Java is very easy to learn, and its syntax is simple, clean and easy
to understand.
 According to Sun Microsystem, Java language is a simple
programming language because:
 Java syntax is based on C++ (so easier for programmers to
learn it after C++).
 Java has removed many complicated and rarely-used features,
for example, explicit pointers, operator overloading, etc.
 There is no need to remove unreferenced objects because there
is an Automatic Garbage Collection in Java.
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Features of JAVA
Object-oriented
 Java is an object-oriented programming language. Everything in
Java is an object. Object-oriented means we organize our software
as a combination of different types of objects that incorporate both
data and behavior.
 Object-oriented programming (OOPs) is a methodology that
simplifies software development and maintenance by providing
some rules.
 Basic concepts of OOPs are:
 Object
 Class
 Inheritance
 Polymorphism
 Abstraction
 Encapsulation
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Features of JAVA
Platform-independent
 Java is platform independent because it is different from other
languages like C, C++, etc. which are compiled into platform
specific machines while Java is a write once, run anywhere
language.
 A platform is the hardware or software environment in which a
program runs.
 The Java platform differs from most other platforms in the sense
that it is a software-based platform that runs on top of other
hardware-based platforms.
 It has two components:
 Runtime Environment
 API(Application Programming Interface)
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Features of JAVA
Platform-independent
Java code can be executed
on multiple platforms, for
example, Windows, Linux,
Sun Solaris, Mac/OS, etc.
Java code is compiled by
the compiler and converted
into
bytecode.
This
bytecode is a platformindependent code because
it can be run on multiple
platforms, i.e., Write Once
and
Run
Anywhere
(WORA).
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Features of JAVA
Secured
Java is best known for its security. With Java, we can develop virusfree systems. Java is secured because:
• No explicit pointer
• Java Programs run inside a virtual machine sandbox
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Features of JAVA
Secured
•
•
•
•
Classloader: Classloader in Java is a part of the Java Runtime
Environment (JRE) which is used to load Java classes into the Java
Virtual Machine dynamically. It adds security by separating the
package for the classes of the local file system from those that are
imported from network sources.
Bytecode Verifier: It checks the code fragments for illegal code that
can violate access rights to objects.
Security Manager: It determines what resources a class can
access such as reading and writing to the local disk.
Java language provides these securities by default. Some security
can also be provided by an application developer explicitly through
SSL, JAAS, Cryptography, etc.
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Features of JAVA
Robust
Java is robust because:
• It uses strong memory management.
• There is a lack of pointers that avoids security problems.
• Java provides automatic garbage collection which runs on the
Java Virtual Machine to get rid of objects which are not being used
by a Java application anymore.
• There are exception handling and the type checking mechanism in
Java. All these points make Java robust.
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Features of JAVA
Architecture-neutral
Java is architecture neutral because there are no implementation
dependent features, for example, the size of primitive types is fixed.
In C programming, int data type occupies 2 bytes of memory for 32bit architecture and 4 bytes of memory for 64-bit architecture.
However, it occupies 4 bytes of memory for both 32 and 64-bit
architectures in Java.
Portable
Java is portable because it facilitates you to carry the Java bytecode
to any platform. It doesn't require any implementation.
High-performance
Java is faster than other traditional interpreted programming
languages because Java bytecode is "close" to native code. It is still
a little bit slower than a compiled language (e.g., C++). Java is an
interpreted language that is why it is slower than compiled
languages, e.g., C, C++, etc.
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Features of JAVA
Distributed
Java is distributed because it facilitates users to create distributed
applications in Java. RMI and EJB are used for creating distributed
applications. This feature of Java makes us able to access files by
calling the methods from any machine on the internet.
Multi-threaded
A thread is like a separate program, executing concurrently. We can
write Java programs that deal with many tasks at once by defining
multiple threads. The main advantage of multi-threading is that it
doesn't occupy memory for each thread. It shares a common
memory area. Threads are important for multi-media, Web
applications, etc.
Dynamic
Java is a dynamic language. It supports the dynamic loading of
classes. It means classes are loaded on demand. It also supports
functions from its native languages, i.e., C and C++.
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JAVA Program life cycle
Java requires the source code of your program to be compiled first. It gets
converted to either machine-specific code or a byte code that is understood
by some run-time engine or a java virtual machine.
Not only will the program be checked for syntax errors by a Java compiler,
but some other libraries of Java code can be added (linked) to your
program after the compilation is complete (deployment stage).
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JAVA Program life cycle
Step1 : Create a source document using any editor and save file as .java (e.g.
abc.java)
Step2 : Compile the abc.java file using “javac” command or eclipse will compile it
automatically.
Step3 : Byte Code (abc.class) will be generated on disk.
Step4 : This byte code can run on any platform or device having JVM (java.exe
convert byte code in machine language)
Let’s get familiar with various terminologies used by java programmers
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JAVA Program life cycle
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JDK, JRE, JVM
Terminologies used in Java Programming
JDK (Java Development Kit): JDK contains JRE along with various
development tools like Java libraries, Java source compilers, Java
debuggers, bundling and deployment tools
JRE (Java Runtime Environment): It is part of JDK but can be used
independently to run any byte code (compiled java program). It can be
called as JVM implementation.
JVM (Java Virtual Machine): ‘JVM’ is software that can be ported to
various hardware platforms. JVM will become an instance of JRE at
runtime of java program. Byte codes are the machine language for the
JVM. Like a real computing machine, JVM has an instruction set which
manipulates various memory areas at run time. Thus for different hardware
platforms, one has corresponding the implementation of JVM available as
vendor supplied JREs.
Java API (Application Programming Interface) : Set of classes’ written
using Java programming language which runs on JVM. These classes will
help programmers by providing standard methods like reading from the
console, writing to the console, saving objects in data structure etc.
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JDK, JRE, JVM
JDK
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JDK, JRE, JVM
JDK
•
•
•
•
•
JDK is an acronym for Java Development Kit.
The Java Development Kit (JDK) is a software development
environment which is used to develop Java applications and applets.
It physically exists, and contains JRE + development tools.
JDK is an implementation of any one of the below given Java Platforms
released by Oracle Corporation:
• Standard Edition Java Platform
• Enterprise Edition Java Platform
• Micro Edition Java Platform
The JDK contains a private Java Virtual Machine (JVM) and a few other
resources such as an interpreter/loader (java), a compiler (javac), an
archiver (jar), a documentation generator (Javadoc), etc. to complete the
development of a Java Application.
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JDK, JRE, JVM
JRE
• JRE is an acronym for Java
Runtime Environment. It is also
written as Java RTE.
• 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.
• The implementation of JVM is
also actively released by other
companies besides Sun Micro
Systems
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JDK, JRE, JVM
JVM
•
•
•
•
•
•
•
•
JVM (Java Virtual Machine) is an abstract machine.
It is called a virtual machine because it doesn't physically exist.
It is a specification that provides a runtime environment in which Java bytecode
can be executed.
It can also run those programs which are written in other languages and compiled
to Java bytecode.
JVMs are available for many hardware and software platforms.
JVM, JRE, and JDK are platform dependent because the configuration of each
OS is different from each other. However, Java is platform independent.
There are three notions of the JVM: specification, implementation, and instance
The JVM performs the following main tasks:
• Loads code
• Verifies code
• Executes code
• Provides runtime environment
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JDK, JRE, JVM
JVM
•
JVM provides definitions for the:
• Memory area
• Class file format
• Register set
• Garbage-collected heap
• Fatal error reporting etc.
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JDK, JRE, JVM
JVM Architecture
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JDK, JRE, JVM
JVM Architecture
Classloader is a subsystem of JVM which is used to load class files.
Whenever we run the java program, it is loaded first by the classloader.
There are three built-in classloaders in Java.
1.Bootstrap ClassLoader: This is the first classloader which is the super
class of Extension classloader. It loads the rt.jar file which contains all class
files of Java Standard Edition like java.lang package classes, java.net
package classes, java.util package classes, java.io package classes,
java.sql package classes etc.
2.Extension ClassLoader: This is the child classloader of Bootstrap and
parent classloader of System classloader. It loads the jar files located
inside $JAVA_HOME/jre/lib/ext directory.
3.System/Application ClassLoader: This is the child classloader of
Extension classloader. It loads the classfiles from classpath. By default,
classpath is set to current directory. You can change the classpath using "cp" or "-classpath" switch. It is also known as Application classloader.
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JDK, JRE, JVM
JVM Architecture
Class(Method) Area
Class(Method) Area stores per-class structures such as the runtime
constant pool, field and method data, the code for methods.
Heap
It is the runtime data area in which objects are allocated.
Stack
Java Stack stores frames. It holds local variables and partial results, and
plays a part in method invocation and return.
Program Counter Register
PC (program counter) register contains the address of the Java virtual
machine instruction currently being executed.
Native Method Stack
It contains all the native methods used in the application.
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JDK, JRE, JVM
JVM Architecture
Execution Engine
It contains:
• A virtual processor
• Interpreter: Read bytecode stream then execute the instructions.
• Just-In-Time(JIT) compiler: It is used to improve the performance. JIT
compiles parts of the byte code that have similar functionality at the
same time, and hence reduces the amount of time needed for
compilation. Here, the term "compiler" refers to a translator from the
instruction set of a Java virtual machine (JVM) to the instruction set of a
specific CPU.
Java Native Interface
Java Native Interface (JNI) is a framework which provides an interface to
communicate with another application written in another language like C,
C++, Assembly etc. Java uses JNI framework to send output to the
Console or interact with OS libraries.
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JAVA-BYTE Code
• In java when you compile a program, the java compiler(javac)
converts/rewrite your program in another form/language which we call
as bytecode.
• The .class file that is generated after compilation is nothing but just the
bytecode instructions of your program.
• The word bytecode and .class are used interchangeably, so if someone
says bytecode, it simply means the .class file of program.
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JAVA-BYTE Code
Byte code
• Byte Code can be defined as an intermediate
code generated by the compiler after the
compilation of source code(JAVA Program).
This intermediate code makes Java a
platform-independent language
• Compiler converts the source code or the
Java program into the Byte Code(or machine
code), and secondly, the Interpreter executes
the byte code on the system.
• The Interpreter can also be called JVM(Java
Virtual Machine). The byte code is the
common piece between the compiler(which
creates it) and the Interpreter (which runs it).
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JAVA-Applications
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•
•
•
•
•
•
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•
•
Mobile Applications
Desktop GUI Applications
Web-based Applications
Enterprise Applications
Scientific Applications
Gaming Applications
Big Data technologies
Business Applications
Distributed Applications
Cloud-based Applications
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JAVA-Programming Structure
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JAVA-Programming Structure
• Need to follow a standard structure for writing the program which is
recommended by the language experts
• A java program may contain many classes of which only one class will
have a main method
• Class will contain data members and methods that operate on the data
members of the class
Example -01
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JAVA-Programming Structure
Package is a collection of classes, interfaces and sub packages. In a java
program if we are using any pre-defined classes and interfaces then it is the
responsibility of the java programmer to import that particular package
containing such specific classes and interface. In java by default java.lang.*
package is imported by every program.
Class is a keyword used for developing user defined data types. Every java
program must starts with a prototype of class. The class has been declared
public, means all classes can access the class from all packages. Generally,
however, we will declare classes in java without specifying a modifier.
Class name is the name given to that class. Every class name is treated as
one kind of user defined data type.
Data Members represents either instance members or static members
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JAVA-Programming Structure
Constructor function is called when an object of the class is created. It is a block of
code that initializes the newly created object. The constructor simply has the same
name as the name of the class name. A constructor does not have a return type.
Constructor and method are different because the constructor is used to initialize the
object of a class while the method is used to perform a task by implementing java
code. Constructors cannot be declared as abstract, final, static and synchronized
while methods can be declared.
Example -2
When we create the object of the bird class as shown above:
bird b = new bird();
The new keyword here creates the object of class bird and invokes the constructor to
initialize this newly created object.
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JAVA-Programming Structure
User-defined methods represent either instance (or) static and they will be selected
depends on the class name and these methods are used for performing the
operations either once (or) repeatedly. All the user-defined methods of a class contain
logic for a specific problem
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JAVA-Programming Structure
User-defined methods
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JAVA-Programming Structure
Main methods
 All java program starts its execution with main() method so main()
method is known as the backbone of the program.
 The Java Virtual Machine starts running any java program by executing
main() method first.
 Java’s main() method is not returning any value so its return type must be
void. Also main() method executes only once throughout the life of the
Java program and before the object creation so its nature must be static.
 The main() method is accessed in all the java programs, its access
specifier must be public (universal).
 Each and every main() method of java must take an array of objects of
String class as an argument.
 The block of statements are set of executable statements written for
calling user-defined methods of the class.
 If we have multiple java files then the naming convention of class file in
java is that, whichever class is containing main() method, that class name
will be given as the file name with an extension (dot) .java.
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JAVA-Programming Structure
Commenting – The compiler ignores comments.
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JAVA-Programming Structure
JAVA – Core Packages
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JAVA-Programming Structure
Importing Classes
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JAVA-Programming Structure
Importing Classes
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JAVA-Programming Structure
Data members
Two types of data members.
1. Instance or non-static data members
2. Static or class data members
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JAVA-Programming Structure
Methods
Two types of methods
1. Instance or non –static methods
2. Static or class method
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JAVA-Programming Structure
Example- 3
“package sct”:
It is package declaration statement. The package statement defines a
namespace in which classes are stored. The package is used to organize the
classes based on functionality. If you omit the package statement, the class
names are put into the default package, which has no name. Package
statement cannot appear anywhere in the program. It must be the first line of
your program or you can omit it.
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JAVA-Programming Structure
2.“public class HelloWorld”:
This line has various aspects of java programming.
a. public: This is access modifier keyword which tells compiler
access to class. Various values of access modifiers can be public,
protected,private or default (no value).
b. class: This keyword used to declare a class. Name of class
(HelloWorld) followed by this keyword.
3. Comments section:
We can write comments in java in two ways.
a. Line comments: It starts with two forward slashes (//) and
continues to the end of the current line. Line comments do not
require an ending symbol.
b. Block comments start with a forward slash and an asterisk (/*) and
end with an asterisk and a forward slash (*/).Block comments can
also extend across as many lines as needed
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JAVA-Programming Structure
4. “public static void main (String [ ] args)”:
Its method (Function) named main with string array as an argument.
a. public: Access Modifier
b. static: static is a reserved keyword which means that a method is
accessible and usable even though no objects of the class exist.
c. void: This keyword declares nothing would be returned from the
method. The method can return any primitive or object.
d. Method content inside curly braces. { } asdfla;sd
5. System.out.println("Hello World from Java") :
a. System: It is the name of Java utility class.
b. out:It is an object which belongs to System class.
c. println: It is utility method name which is used to send any String
to the console.
d. “Hello World from Java”: It is String literal set as argument to
println method
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JAVA-Programming Structure
Prog Exercise 01
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JAVA-Programming Structure
Prog Exercise 02
classMember.java
// Java code to show structures and
// members of Java Program
public class classMember
{
// Static member
static int staticNum = 0;
// Instance member
int instanceNum;
/* below constructor increments the static
number and initialize instance number */
public classMember(int i) //Constructor method
{
instanceNum = i;
staticNum++;
}
/* The show method display the value in the staticNum and
instanceNum */
public void show() //instance method
System.out.println("Value of Static Number is:" + staticNum +
"\nValue of Instance number is:"+ instanceNum);
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JAVA-Programming Structure
// To find cube
public static int cube() //Static method
{
return staticNum * staticNum * staticNum;
}
// Driver code
public static void main(String args[])
{
classMember gvp1 = new classMember(2);
System.out.println("Value after gvp1 object
creation: ");
gvp1.show();
classMember gvp2 = new classMember(4);
System.out.println("Value after gvp2 object
creation: ");
gvp2.show();
// static method can be accessed by class name
int cub=classMember.cube();
System.out.println("Cube of the Static number is: "+
cub);
}
}
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References
•
•
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•
•
https://www.javatpoint.com/
https://www.geeksforgeeks.org/
https://www.w3schools.com/
https://www.educba.com/
Y. Daniel Liang, Intro to Java Programming,
Pearson Education India
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THANK YOU !!
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