JAVA CORE

A Seminar report
On
JAVA CORE
Submitted in Partial Fulfillment of requirements for the Award of Degree of
BACHELOR OF TECHNOLOGY
In
ELECTRONICS AND COMMUNICATION ENGINEERING
Submitted by
ANKIT CHAUHAN (1409031005)
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING
IEC COLLEGE OF ENGINEERING AND TECHNOLOGY,
GREATER NOIDA
Dr. A.P.J. ABDUL KALAM TECHNICAL UNIVERSITY, LUCKNOW
Submitted to:
Mr. Shashank

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ACKNOWLEDGEMENT
I have taken efforts in this project. However, it would not have been possible without the kind
support and help of many individuals and organizations. I would like to extend my sincere thanks
to all of them.
I am highly indebted to Incapp Infotech for their guidance and constant supervision as well as
for providing necessary information regarding the project & also for their support in completing
the project.
I would like to express my gratitude towards my parents & member for their kind co-operation
and encouragement which help me in completion of this project.
I would like to express my special gratitude and thanks to industry persons for giving me such
attention and time.
My thanks and appreciations also go to my colleague in developing the project and people who
have willingly helped me out with their abilities.

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INDEX
S. No TOPIC NAME
PAGE NO.
1 Introduction To Java 4
2
The Java Platform
5
3 Installation Of Java 6
4 Configuring Variable 8
5 Write, Compile And Run a Java Program 10
6
Package
12
7 Class And Object 13
8
Inheritance
14
9 Variable And Method 16
10 Modifiers And Import Statement 19
11
Interface
21
12 Working With Classes 23
13 IDE 27
14 History of Java 41
15 Features of Java 44

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Introduction to Java
With the invention of microprocessors, the world is scientifically developed with sophisticated
equipments, systems, and devices. Microprocessors are used in computers, televisions, and fax
machines. Even the hand-held devices such as pagers, PDAs (Personal Digital Assistant), and
cell phones make use of microprocessors. All these electronic devices are helpful because of
their communication capabilities. With the increasing capabilities and decreasing cost of
information processing and networking technologies, the network is growing rapidly for
transmitting information through electronic systems.
Internet is the network of networks between different types of computers located at
different places to transmit information. Information can reach to any place in the world quickly
at a cheaper rate through the Internet. Thus, the Internet has made the world a global village for
information exchange. The emerging infrastructure of electronic devices and interconnected
computer networks create an environment that presents new challenges to software industries.
for this emerging computing environment, Java process to be a well – suited programming
language. it is found suitable for networked environments involving a great variety of computer
and devices.
Java has many characteristics that have contributed to its popularity:
 Platform independence - Many languages are compatible with only one platform. Java
was specifically designed so that it would run on any computer, regardless if it was
running Windows, Linux, Mac, Unix or any of the other operating systems.
 Simple and easy to use - Java's creators tried to design it so code could be written
efficiently and easily.
 Multi-functional - Java can produce many applications from command-line programs to
applets to Swing windows (basically, sophisticated graphical user interfaces).
Java does have some drawbacks. Since it has automated garbage collection, it can tend to use
more memory than other similar languages. There are often implementation differences on
different platforms, which have led to Java being described as a "write once, test everywhere"
system. Lastly, since it uses an abstract "virtual machine", a generic Java program doesn't have
access to the Native API's on a system directly. None of these issues are fatal, but it can mean
that Java isn't an appropriate choice for a particular piece of software.

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The Java Platform
One thing that distinguished Java from some other languages is its ability to run the same
compiled code across multiple operating systems. In other languages, the source code (code that
is written by the programmer), is compiled by a compiler into an executable file. This file is in
machine language, and is intended for a single operating system/processor combination, so the
programmer would have to re-compile the program seperately for each new operating
system/processor combination. Java is different in that it does not compile the code directly into
machine language code. Compilation creates bytecode out of the source code. Bytecode
generally looks something like this:
a7 f4 73 5a 1b 92 7d
When the code is run by the user, it is processed by something called the Java Virtual Machine
(JVM). The JVM is essentially an interpreter for the bytecode. It goes through the bytecode and
runs it. There are different versions of the JVM that are compatible with each OS and can run the
same code. There is virtually no difference for the end-user, but this makes it a lot easier for
programmers doing software development.
Java and Open Source:-
 In 2006 Sun started to make Java available under the GNU General Public License
(GPL). Oracle continues this project called OpenJDK.
Java Virtual Machine:-
 The Java virtual machine (JVM) is a software implementation of a computer that
executes programs like a real machine.
 The Java virtual machine is written specifically for a specific operating system, e.g. for
Linux a special implementation is required as well as for Windows.
 Java programs are compiled by the Java compiler into bytecode. The Java virtual machine
interprets this bytecode and executes the Java program.
Java Runtime Environment vs. Java Development Kit
 A Java distribution comes typically in two flavors, the Java Runtime Environment (JRE)
and the Java Development Kit (JDK).
 The Java runtime environment (JRE) consists of the JVM and the Java class libraries and
contains the necessary functionality to start Java programs.
 The JDK contains in addition the development tools necessary to create Java programs.
The JDK consists therefore of a Java compiler, the Java virtual machine, and the Java
class libraries.

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Installation of Java
 Check installation
 Java might already be installed on your machine. You can test this by opening a console
(if you are using Windows: Win+R, enter cmd and press Enter) and by typing in the
following command:
 java -version
 If Java is correctly installed, you should see some information about your Java
installation. If the command line returns the information that the program could not be
found, you have to install Java.
Installing the Java Development Kit
 Before installing the Java Development Kit (JDK), you should probably know what it is.
It is distributed by Oracle. It contains the core libraries and compiler required to develop
Java. The JDK should not be confused with the JRE (Java Runtime Environment). The
JRE is a JVM for running, as opposed to compiling, Java programs.
Downloading and Installing
 To download the JDK, go to
http://www.oracle.com/technetwork/java/javase/downloads/index.html. Click on "JDK
with NetBeans Bundle". Follow the instructions for downloading the JDK installation
file.
Windows: If you are running Windows, simply run the executable file and follow the
installation instructions.
Unix, Solaris, or Linux: For Linux and Unix, download the "jdk1 6.0" for Linux
systems. Save the downloaded file in any drive. Once you have saved the file, extract it to
a place that you can remember, by using Terminal or by double clicking on the file.
When you have finished extracting the file, copy the JDK 1.6.0 folder and paste it in the
usr/local(To paste to the usr/local directory, you have to be in root) so that every user can
use the java files. You can delete the downloaded zip file so that it doesn't take up space
on your drive.
Macintosh: The latest available JDK is automatically installed by the operating
system. Because Java for Macintosh is developed and maintained by Apple, in
coordination with Sun, the current version on the Macintosh may not be the current
version that is available
Note on Editions
 The JDK comes in three editions.
 Java Standard Edition (JSE) – This version is the basic platform for Java. The course will
focus on this edition.

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 Java Enterprise Edition (JEE) – This edition is mainly for developing and running
distributed multitier architecture Java applications, based largely on modular software
components running on an application server. We will not be covering this version in the
course.
 Java Micro Edition (JME) – This edition is primarily for developing programs to run on
consumer applicances, such as PDAs and cell phones.

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Configuring Variables
 Before writing code, it is recommended that you set the Path variable on your system
so you can compile your code more easily.
For Windows Users
 From the Control Panel, double click "System" (System and Maintenance in Vista)
 For Windows 7 or Vista, click on "System," "Advanced System Settings" on the left, and
then on "Environment Variables."
 For XP and 2000, click on the "Advanced" tab and click on "Environment Variables" For
NT, click on the "Environment" tab.
 Select the Path variable and click "Edit"
 Add the path to the bin directory of where Java is installed on your hard drive. It should
probably be: C:Program FilesJavajdk1.6.0_20bin unless you changed it during
installation.
 Click OK
For Linux and UNIX
 One way to set your path in Linux/Unix is to add a path export to your bash profile.
 In order to do this, first open your bash profile in a text editor. For example,
 pico ~/.bash_profile
 Then add this line:
 export PATH=$PATH:/usr/local/jdk/bin
 Note that the path to the java directory "/usr/local/jdk/bin" may be different on your
machine.
 Restart your shell.
For Macintosh
 Apple sets everything up for you. Sit back and relax.
 The only drawback is that because Apple handles development and maintenance of Java
on the Mac, there is usually a delay from the time that a new version is released by Sun
and the time that the new version is released on the Mac. Also, getting the latest version
sometimes requires an operating system upgrade.
 Oh well, you can't have everything.

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Validate installation
 Switch again to the command line and run the following command.
 java -version
 The output should be similar to the following output.
 java version "1.7.0_25"
 OpenJDK Runtime Environment (IcedTea 2.3.10) (7u25-2.3.10-1ubuntu0.13.04.2)
 OpenJDK 64-Bit Server VM (build 23.7-b01, mixed mode)
Development Process with Java
 Java source files are written as plain text documents. The programmer typically writes
Java source code in an Integrated Development Environment (IDE) for programming. An
IDE supports the programmer in the task of writing code, e.g. it provides auto-formating
of the source code, highlighting of the important keywords, etc.
 At some point the programmer (or the IDE) calls the Java compiler (javac). The Java
compiler creates the bytecode instructions. These instructions are stored in .class files
and can be executed by the Java Virtual Machine.
Garbage collector
 The JVM automatically re-collects the memory which is not referred to by other objects.
The java garbage collector checks all object references and find the objects which can be
automatically released.
 While the garbage collector releases the programmer from the need to explicitly manage
memory the programmer still need to ensure that he does not keep unneeded object
references otherwise the garbage collector cannot release the associated memory.
Keeping unneeded object references are typically called memory leaks.
Classpath
 The classpath defines where the Java compiler and Java runtime look for .class files to
load. This instructions can be used in the Java program.
 For example if you want to use an external Java library you have to add this library to
your classpath to use it in your program.

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Write, compile and run a Java program
Write source code
 The following Java program is developed under Linux using a text editor and the
command line. The process on other operating system should be similar and but is not
covered in this description.
 Select or create a new directory which will be used for your Java development. In this
description the path homevogellajavastarter is used. On Microsoft Windows your
might want to use c:tempjavastarter. This path is called javadir in the following
description. Open a text editor which supports plain text, e.g. gedit under Linux or
Notepad under Windows and write the following source code.
Fig.1
 Save the source code in your javadir directory with the HelloWorld.java filename. The
name of a Java source file must always equals the class name (within the source code)
and end with the .java extension. In this example the filename must be
HelloWorld.java because the class is called HelloWorld.
 Compile and run your Java program
 Open a shell for command line access. Switch to the javadir directory with the
command cd javadir, for example in the above example via the cd
homevogellajavastarter command. Use the ls command (dir under Microsoft
Windows) to verify that the source file is in the directory. Compile your Java source file
into a class file with the following command.

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Javac HelloWorld.java
Afterwards list again the content of the directory with the ls or dir command. The
directory contains now a file "HelloWorld.class". If you see this file you have
successfully compiled your first Java source code into bytecode.
You can now start your compiled Java program. Ensure that you are still in the jardir
directory and enter the following command to start your Java program.
java HelloWorld
The system should write "Hello World" on the command line.
Fig.2
Using the classpath
 You can use the classpath to run the program from another place in your directory.
 Switch to the command line, e.g. under Windows Start-> Run -> cmd. Switch to any
directory you want. Type:
java HelloWorld
 If you are not in the directory in which the compiled class is stored then the system
should result an error message Exception in thread "main"
java.lang.NoClassDefFoundError: test/TestClass
 To use the class type the following command. Replace "mydirectory" with the directory
which contains the test directory. You should again see the "HelloWorld" output.
java -classpath "mydirectory" HelloWorld
Java basic terms

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 Basics: Package, Class and Object
It is important to understand the base terminology of Java in terms of packages, classes and
objects. This section gives an overview of these terms.
 Package
Java groups classes into functional packages.
Packages are typically used to group classes into logical units. For example all graphical
views of an application might be placed in the same package called
com.vogella.webapplication.views.
It is common practice to use the reverse domain name of the company as top level package.
For example the company might own the domain, vogella.com and in this example the Java
packages of this company starts with com.vogella.
Other main reason for the usage of packages is to avoid name collisions of classes. A name
collision occurs if two programmers give the same fully qualified name to a class. The fully
qualified name of a class in Java consists out of the package name followed by a dot (.) and
the class name.
Without packages, a programmer may create a Java class called Test. Another programmer
may create a class with the same name. With the usage of packages you can tell the system
which class to call. For example if the first programmer puts the Test class into package
report and the second programmer puts his class into package xmlreader you can
distinguish between these classes by using the fully qualified name, e.g. xmlreader.Test or
report.Test.

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 Class
Def.: Template that describes the data and behavior associated with an instance of that
class.
In Java source code a class is defined by the class keyword and must start with a capital
letter. The body of a class is surrounded by {}.
package test;
class MyClass {
}
The data associated with a class is stored in variables ; the behavior associated to a class
or object is implemented with methods.
A class is contained in a Java source file with the same name as the class plus the .java
extension.
 Object
Def.: An object is an instance of a class.
The object is the real element which has data and can perform actions. Each object is
created based on the class definition.

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 Inheritance
A class can be derived from another class. In this case this class is called a subclass. Another
common phrase is that a class extends another class.
The class from which the subclass is derived is called a superclass.
Inheritance allows a class to inherit the behavior and data definitions of another class.
The following codes demonstrates how a class can extend another class. In Java a class can
extend a maximum of one class.
package com.vogella.javaintro.base;
class MyBaseClass {
void hello(){
System.out.println("Hello from MyBaseClass");
}
}
class MyExtensionClass extends MyBaseClass {
}
 Override methods and the @override annotation
If a class extends another class it inherits the methods from its superclass. If it wants to
change these methods it can override these methods. To override a method you use the same
method signature in the source code of the subclass.
To indicate to the reader of the source code and the Java compiler that you have the intention
to override a method you can use the @override annotation.
The following code demonstrates how you can override a method from a superclass.
class MyBaseClass {
void hello(){
System.out.println("Hello from MyBaseClass");
}
}
class MyExtensionClass2 extends MyBaseClass {
}
Object has superclass

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Every object in Java implicitly extends the Object class. The class defines the following
methods for every Java object:
 equals(o1) allows to check if the current object is equal to o1
 getClass() returns the class of the object
 hashCode() returns an identifier of the current object
 toString() Give a string representation of the current object

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Variables and methods
 Variable
Variables allow the Java program to store values during the runtime of the program.
A variable can either be a primitive variable or a reference variable. A primitive variable
contains value while the reference variable contains a reference (pointer) to the object.
Hence if you compare two reference variables, you compare if both point to the same object.
To compare objects use the object1.equals(object2) method call.
 Instance variable
Instance variable is associated with an instance of the class (also called object). Access
works over these objects.
Instance variables can have any access control and can be marked final or transient. Instance
variables marked as final can not be changed after assigned to a value.
 Local variable
Local (stack) variable declarations cannot have access modifiers.
final is the only modifier available to local variables. This modifier defines that the variable
can not be changed after first assignment.
Local variables do not get default values, so they must be initialized before use.
 Methods
A method is a block of code with parameters and a return value. It can be called on the
object.
public class MyMethodExample {
void tester(String s) {
System.out.println("Hello World");
}
}

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Method can be declared with var-args. In this case the method declares a parameter
which accepts from zero to many arguments (syntax: type .. name;) A method can only
have one var-args parameter and this must be the last parameter in the method.
Overwrite of a superclass method: A method must be of the exact same return parameter
and the same arguments. Also the return parameter must be the same. Overload methods:
An overloaded method is a method with the same name, but different arguments. The
return type can not be used to overload a method.
 Main method
A public static method with the following signature can be used to start a Java
application. Such a method is typically called main method.
public static void main(String[] args){
}
 Constructor
A class contains constructors that are invoked to create objects based on the class
definition. Constructor declarations look like method declarations except that they use the
name of the class and have no return type. A class can have several constructors with
different parameters. Each class must define at least one constructor.
In the following example the constructor of the class expects a parameter.
public class MyConstructorExample2 {
String s;
public MyConstructorExample2(String s) {
this.s = s;
}
}
If no explicit constructor is defined the compiler adds implicitly a constructor. If the class
is sub-classed then the constructor of the super class is always implicitly called in this
case.
In the following example the definition of the constructor without parameters (also
known as the empty constructor) is unnecessary. If not specified the compiler would
create one.

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public class MyConstructorExample {
// Unnecessary, would be created by the compiler if left out
public MyConstructorExample() {
}
}
The naming conversion for creating a constructor is the following: classname
(Parameter p1, ..) {} .
Every object is created based on a constructor. This constructor method is the first
statement called before anything else can be done with the object.

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Modifiers
 Access modifiers
There are three access modifiers keywords available in Java. public, protected and private.
There are four access levels: public, protected, default and private. They define how the
corresponding element is visible to other components. If something is declared public, e.g.
classes or methods can be freely created or called by other Java objects. If something is
declared private, e.g. a method, it can only be accessed within the class in which it is
declared. protected and default are similar. A protected class can be accessed from the
package and sub-classes outside the package while a default class can get only accessed via
the same package. The following table describes the visibility:
Table 1. Access Level
Modifier Class Package Subclass World
Public Y Y Y Y
protected Y Y Y N
no
modifier
Y Y N N
Private Y N N N
Other modifiers
 final methods: cannot be overwritten in a subclass
 abstract method: no method body
 synchronized method: threat safe, can be final and have any access control
 native methods: platform dependent code, apply only to methods
 strictfp: class or method
Import statements
 Usage of import statements
In Java you have to access a class always via its full-qualified name, e.g. the package
name and the class name. You can add import statements for classes or packages into

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your class file, which allow you to use the related classes in your code without the
package qualifier.
 Static imports
Static import is a feature that allows members (fields and methods) which are defined in a
class with the public static access modifier to be used in Java code without specifying
the class in which the member is defined. The feature provides a typesafe mechanism to
include constants into code without having to reference the class that originally defined the
field.

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More Java language constructs
 Interface
Interfaces are contracts for what a class can do but they say nothing about the way in
which the class must do it. An interface is a type similar to a class. Like a class an
interface defines methods. An interface can have only abstract methods, no concrete
methods are allowed. Methods defined in interfaces are by default public and abstract –
explicit declaration of these modifiers is optional. Interfaces can have constants which are
always implicitly public, static and final. A class can implement an interface. In this case
it must provide concrete implementations of the interface methods. If you override a
method defined by an interface you can also use the @override annotation. The
following code shows an example implementation of an interface and its usage within a
class.
public interface MyDefinition {
// constant definition
String URL="http://www.vogella.com";
// define several method stubs
void test();
void write(String s);
}
public class MyClassImplementation implements MyDefinition {
@Override
public void test() {
// TODO Auto-generated method stub
}
@Override
public void write(String s) {
// TODO Auto-generated method stub
}
}
Class methods and class variables
Class methods and class variables are associated with the class and not an instance of the
class, i.e. objects. To refer to these element you can use the classname and a dot (".")
followed by the class method or class variable name. Class methods and class variables
are declared with the static keyword. Class methods are also called static methods and
class variables are also called static variables or static fields.

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An example for the usage of a static field is println of the following statement:
System.out.println("Hello World"). out is a static field, an object of type
PrintStream, and you call the println() method on this object. If you define a static
variable the Java runtime environment associates one class variable for a class no matter
how many instances (objects) exists. The static variable can therefore be seen as a global
variable. The following code demonstrates the usage of static fields.
public class MyStaticExample {
static String PLACEHOLDER = "TEST";
static void test() {
System.out.println("Hello");
}
}
public class Tester {
public static void main(String[] args) {
System.out.println(MyStaticExample.PLACEHOLDER);
MyStaticExample.test();
}
}
If a variable should be defined as constant, you declare it with the static and the final
keyword. The static method runs without any instance of the class, it cannot directly
access non-static variables or methods.
 Abstract class and methods
A class and method can be declared as abstract. An abstract class can not be directly
instantiated. If a class has at least one method which only contain the declaration of the
method but not the implementation then this class is abstract and can not be
instantiated. Sub-classes need then to define the methods except if they are also declared
as abstract. If a class contains an abstract method it also needs to get defined with the
keyword abstract. The following example shows an abstract class.
public abstract class MyAbstractClass {
abstract double returnDouble();
}

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Working With Classes
Table 2
What to do How to do it
Create a new class called MyNewClass.
package test;
public class MyNewClass {
}
Create a new attribute (instance variable)
called var1 of type String in the MyNewClass
class
package test;
private String var1;
}
Create a Constructor for your MyNewClass
class which has a String parameter and assigns
the value of it to the var1 instance variable.
package test;
public MyNewClass(String
para1) {
var1 = para1;
// or this.var1= para1;
}
}
Create a new method called doSomeThing in
your class which does not return a value and
has no parameters
package test;
para1) {
var1 = para1;
}
public void doSomeThing()
{
}
}
Create a new method called doSomeThing2 in
your class which does not return a value and
has two parameters, a int and a Person
package test;
para1) {
var1 = para1;

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}
{
}
public void
doSomeThing2(int a, Person
person) {
}
}
Create a new method called doSomeThing2 in
your class which returns an int value and has
three parameters, two Strings and a Person
package test;
para1) {
var1 = para1;
}
{
}
public void
doSomeThing2(int a, Person
person) {
}
public int
doSomeThing3(String a,
String b, Person person) {
return 5; // Any value
will do for this example
}
}
Create a class called MyOtherClass with two
instance variables. One will store a String, the
other will store a Dog. Create getter and setter
for these variables.
package test;
public class MyOtherClass {
String myvalue;
Dog dog;
public String
getMyvalue() {
return myvalue;
}

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public void
setMyvalue(String myvalue)
{
this.myvalue = myvalue;
}
public Dog getDog() {
return dog;
}
public void setDog(Dog
dog) {
this.dog = dog;
}
}
Working With Local Variable
Table 3:
Declare a (local) variable of type string. String variable1;
Declare a (local) variable of type string and assign
"Test" to it.
String variable2 = "Test";
Declare a (local) variable of type Person Person person;
Declare a (local) variable of type Person, create a
new Object and assign the variable to this object.
Person person = new Person();
Declare a array of type String String array[];
Declare a array of type Person and create an array
for this variable which can hold 5 Persons.
Person array[]= new Person[5];
Assign 5 to the int variable var1 (which was
already declared);
var1 = 5;
Assign the existing variable pers2 to the exiting
variable pers1;
pers1 = pers2;
Declare a ArrayList variable which can hold
objects of type Person
ArrayList<Person> persons;
Create a new ArrayList with objects of type
Person and assign it to the existing variable
persons
persons = new
ArrayList<Person>();

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Declare a ArrayList variable which can hold
objects of type Person and create a new Object for
it.
ArrayList<Person> persons =
new ArrayList<Person>();

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Integrated Development Environment
The previous chapter explained how to create and compile a Java program on the
command line. A Java Integrated Development Environment (IDE) provides lots of ease
of use functionality for creating java programs. There are other very powerful IDE's
available, for example the Eclipse IDE. . For an introduction on how to use the Eclipse
IDE please see Eclipse IDE Tutorial. The remaining description uses the phrase: Create a
Java project called... ". This refers to creating a Java project in Eclipse. If you are using a
different IDE please follow the required steps in this IDE. Exercises - Creating Java
objects and methods Create a Person class and instantiate it Create a new Java project
called com.vogella.javastarter.exercises1 and a package with the same name. Create a
class called Person. Add three instance variables to it, one for storing the first name of the
person, on for storing the last name and one for storing the age of the Person. Use the
constructor of the Person object to set the values to some default value. Write a public
method called writeName() which uses the System.out.println( method to print the first
name of the person to the console. Create a new class called Main with a public static
void main(String[] args). In this method create an instance of the Person class.
 Use constructor
Add a constructor to your Person class which takes the first name, last name and the age
as parameter. Assign the values to your instance variables. Create in your main method
two objects of type Person and call the writeName method on it.
 Define getter and setter methods
Define methods which allow you to read the values of the instance variables and to set them.
These methods are called setter and getter. Getters should start with get followed by the
variable name whereby the first letter of the variable is capitized. Setter should start with set
followed by the variable name whereby the first letter of the variable is capitized. ` For
example the variable called firstName would have the getFirstName() getter method and the
setFirstName(String s) setter method. Change your main method so that you create one
person object and use the setter method to change the last name.
 Create an Address object
Create a new object called Address. The Address should allow you to store the address of a
person. Add a new instance variable of this type in the Person object. Also create a getter
and setter for the Address object in the Person object.

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Solution - Creating Java objects and methods
Create a Person class and instantiate it
The following is a potential solution for Section 11.1, “Create a Person class and instantiate
it”.
package exercises.exercise04;
class Person {
String firstname = "Jim";
String lastname = "Knopf";
int age = 12;
voi d writeName() {
// Writes the firstname
System.out.println(firstname);
// Alternatively you can combine strings with +
System.out.println(firstname + " " + lastname + "" + age);
}
}
package exercises.exercise04;
public class Main {

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Person person = new Person();
}
person.writeName();
}
Use constructor
package com.vogella.javastarter.exercises1;
class Person {
String firstName;
String lastName;
int age;
public Person(String a, String b, int value) {
firstName = a;
lastName = b;
age=value;
}
void writeName() {
System.out.println(firstName);

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System.out.println(firstName + " " + lastName + "" + age);
}
}
public class Main {
void main(String[] args) {
Person person = new Person("Jim", "Knopf" , 12);
person.writeName();
// Reuse the same variable and assign new object to it
person = new Person("Henry", "Ford", 104);
person.writeName();
}
}

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Define getter and setter methods
class Person {
String firstName;
String lastName;
int age;
firstName = a;
lastName = b;
age = value;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {

- 32 -
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
void writeName() {
}

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}
public class Main {
Person person = new Person("Jim", "Knopf", 21);
Person person2 = new Person("Jill", "Sanders", 20);
// Jill get married to Jim
person2.setLastName("Knopf");
person2.writeName();
}
}

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Create an Address object
public class Address {
private String street;
private String number;
private String postalCode;
private String city;
private string country;
public String getStreet() {
return street;
}
public void setStreet(String street) {
this.street = street;
}
public String getNumber() {
return number;
}

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public void setNumber(String number) {
this.number = number;
}
public String getPostalCode() {
return postalCode;
}
PostalCode(String postalCode) {
this.postalCode = postalCode;
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public String getCountry() {
return country;
}

- 36 -
public void setCountry(String country) {
this.country = country;
}
public String toString() {
return street + " " + number + " " + postalCode + " " + city + " "
+ country;
}
}
class Person {
String firstName;
String lastName;
int age;
private Address address;
firstName = a;
lastName = b;

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age=value;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public int getAge() {
return age;
}

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public void setAge(int age) {
this.age = age;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
void writeName() {
}
}

- 39 -
public class Main {
// I create a person
Person pers = new Person("Jim", "Knopf", 31);
// I set the age of the person to 32
// Just for testing I write this to the console
System.out.println(pers.toString());
/*
* Actually System.out.println calls always toString, if you do not
* specify it so you could also have written System.out.println(pers);
*/
// I create an address
Address address = new Address();
// I set the values for the address
address.setCity("Heidelberg");
address.setCountry("Germany");
address.setNumber("104");
address.setPostalCode("69214");
address.setStreet("Musterstr.");

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address = null;
// person is moving to the next house in the same street
pers.getAddress().setNumber("105");
}
}

- 41 -
HISTORY OF JAVA
It is quite interesting to know the development of Java technology, which is widely accepted in
the area of networked/distributed computing. Java evolved from a project developing a language
for programming consumer electronic devices at Sun Microsystems, USA.
Sun’s Stealth Project in 1990 was aimed to do research in the area of application of
computers in the consumer electronics market. Bill Joy, James Gosling, Mike Sheridan, Patrick
Naughton (formerly the project leader of Sun’s Open Windows user environment), and several
other individuals discussed the ideas for the Stealth Project in January 1991.The vision of this
project was to develop smart consumer electronic devices that could all be centrally controlled
and programmed from a handheld-remote-control-like device. The Stealth group began to work
to achieve this goal. It was realized that a platform-independent development-environment was
needed.
Green Project was initiated by Patrick Naughton, Mike Sheridan, and James Gosling of
Sun Microsystems in 1991 (Members of the Stealth Project, which later became known as the
Green Project) The tasks of the project were divided amongst the members of Green Project.
Mike Sheridan concentrated on business development, Patrick Naughton worked on the graphics
system, and James Gosling was to identify the appropriate programming language for the Green
Project. Even though creating a new language was not the aim of Green Project, a new language
was created as a programming tool in this project since C++ was found unsuitable for the project.
An intelligent remote control called *7 (Star Seven) was delivered as the first product of
Green Project in 1992. It is a PDA- like device comprising of a new language oak, an operating
system called GreenOS, user interface, and hardware. This device was quite impressive to Sun
Executives. But no customer was interested in this project. The market was not conducive to this
type of device in the consumer electronics industry.
The new language Oak was created by James Gosling, a Green Team member,
specifically for *7. Gosling named the new language Oak because that name was struck while
looking at an oak three outside of his office window. The name Oak was later renamed to Java
in order to avoid legal issues since Oak was the name of an existing language.
In November 1992, the Green Project was incorporated under the name FirstPerson. In
1993. Time-Warner was demanding for proposals for set-top box operating systems and video-
on-demand technology with an objective of sending the data to consumer all over the country for
display on the television sets. At the same time (1993(, NCSA released the first graphical web
browser Mosaic 1.0, an easy-to-use front end to the World Wide Web.
When FirstPerson was bidding on the Time-Warner TV trial based on video-on-demand
technology, Time-Warner chose Silicon Graphics, Inc. (SGI) over Sun. Hence, half of the
members of FirstPerson left for SGI and the remaining members continued to work at Sun.

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Mosaic web browser revolutionized people’s perceptions. The remaining member of
FirstPerson returned to work on Java (Oak was renamed Java) to develop Java-based web
browser. FirstPerson was dissolved gradually. Naughton and Jonathan Payne developed
WebRunner (named after the movie Blade Runner). Later WevRunner was officially announced
as the HotJavaTM browser in 1994. This was the turning point for Java. At that time the World
Wide Web changed the face of Internet and it was winning the race on Internet.
Arthur Ban Hoff implemented the Java compiler in Java itself whereas Gosling
implemented it in C. The Java compiler, written in Java made the people to accept Java as a full-
featured language.
Sun Microsystems officially announced Java environment at Sun World’95 on May 23,
1995. Java entered into the mainstream of the Internet after a struggle for about four years.
Netscape Communications incorporated Java into its web browser Netscape Navigator. Within a
decade, Java was destined to be the most overreaching technology in the Internet. Java was not
restricted to the Internet alone. The initial goal of Sun was also achieved by using Java
technology in interactive set-top boxes, hand-held devices and other consumer electronics
products.
Sun released the first version 1.0 of Java in 1996. Java is an object-oriented programming
language which evolved from C++. It is also a high-level programming language. The different
forms of Java versions are discussed in the next section.
History of Java
Year Java - Versions and Features
1990 Sun Microsystems started Stealth project supporting application of computers in the
consumer electronics market.
1991 The Green project started with the members of Stealth project such as James Gosling,
Patrick Naughton, and Mike Sheridan. A new programming language, called Oak was
created by Gosling.
1992 An intelligent remote control called StarSeven was delivered. The Green Project was
incorporated was incorporated under the name FirstPerson.
1993 Mosaic Web browser was introduced in the world of Internet.
1994 HotJava Web browser was announced by Sun Microsystems.
1995 Oak was renamed as Java. Sun officially announced Java technology.
1996 Sun released the first version 1.0 of Java. Core Language features supporting: I/O
facility, Utilities, Network Programming, User Interface – AWT, Applets, and
Multithreading.
1997 Sun released JDK1.1 by including new features such as addition of inner classes to
the language and capabilities such as JavaBeans, JDBC(Java Data Base
Connectivity), and RMI (Remote Method Invocation).
1998 Java 2 Platform, Standard Edition (J2SE)1.2, code named as Playground, was
released. It replaced JDK and distinguished the base platform from j2ee (Java 2
Platform, Enterprose Edition) and J2ME (Java 2Platform, Micro Edition). The key
features include Swing graphical API, Java IDL (Interface Definition Language) to
support CORBA interoperability. They also added Collections framework to support
various data structures. For the first time, JVM was equipped with a JIT (Just-in-

- 43 -
Time) compiler.
2000 J2SE 1.3, code named as Kestrel, was released with key features such as JavaSound
API to support audio operations (e.g., audio playback and capture/recording, mixing,
sequencing, and synthesis), Java Naming and Directory Interface (JNDI), and Java
Platform Debugger Architecture (JPDA).
2002 H2SE 1.4, code named as Merlin, was released with key features such as (a) image
I/O API for manipulating images in formats like JPEG and PNG, (b) integrated XML
parser and XSLT processor (JAXP), integrated security and cryptography extensions,
(c) Java Web Start supporting deployment of Java software applications over the
network.
2004 J2SE 5.0, code named as Tiger, was released with enhancement of Java platform and
inclusion of a number of significant new language features such as Generics,
Enhanced for Loop, Autoboxing/Unboxing, Typesafe Enums, Varags, Static Import,
and Metadata supporting declarative style programming annotation of source code.
2006 Java SE 6.0, code named as Mustang, was released with enhancement of performance
in Swing, JDBC 4.0 support, Java Compiler API, Upgrade of JAXB to version 2.0,
including integration of a StAX parser, support for pluggable annotations, and many
GUI improvements.
2008 Java SE 7.0, code named as Dolphin, with native support for XML recognizing its
foundation for Web services.

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FEATURES OF JAVA
According to Sun, Java is defined as a simple, object-oriented, distributed, interpreted, robust,
secure, architecture –neutral, portable, high performance, multithreaded, and dynamic
programming language and platform.
Java is simple because the syntax of well-known languages such as C and C++ are used with
modifications meant for simplification and improvement. It is easy to read and write Java code if
the reader is familiar with C/C++.
Almost everything in Java is centered on creating objects, manipulating the objects and making
objects work together. Only the primitive operations and data types are at the sub-object level.
Hence Java is an object-oriented programming language.
An application can be distributed in many systems which are connected together. Since
networking capability is incorporated in Java, the data/file can be sent across many systems to
run the application.
Java is robust because it is more reliable. It ensures the reliability by providing early checking
for possible errors. It eliminates error-prone constructs such as pointer. It eliminates error-prone
constructs such as pointer. It also supports runtime error handling.
Java programs are compiled to a byte code format that can be read and run by interpreters on
many platforms including Windows, Linux, etc. Hence, it is architecture neutral. Because of this
feature it is portable to new hardware and operating systems.
Although the speed of execution of Java programs is slower compared to C/C++ programs, Java
is meant for distributed applications. Whenever the file/data is transmitted from one system to
another, the performance is not affected. Hence, it is having high performance.
Java supports multithreaded programming to perform several tasks simultaneously. Any code
can be loaded without recompilation at runtime. Hence it is dynamic.

JAVA CORE

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