Programming in

Java
Revised 2nd Edition
Sachin Malhotra & Saurabh Choudhary

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Chapter 2
Getting started with Java

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 Objective
• Know the Java Features and its Runtime Environment

• Get familiar with new releases in Java

• Understand the basic structure of a Java program

• Get into the details about JDK Installation

• Know about the various constituents of JDK and its development

environments

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 Introduction
• Java is a programming language developed by James Gosling and
others in 1994.

• Originally named Oak ,was developed as a part of the Green project

at Sun Microsystems.

• Java 9 is latest stable release.

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 Java Essentials
• A high level language

• Java Bytecode – intermediate code

• Java Virtual Machine (JVM) – interpreter for bytecode

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 Java Runtime
Java Runtime Environment includes JVM, class libraries and other
supporting files.
JAVA SOURCE CODE

Compilation
JAVA BYTE CODE

Interpretation
JAVA VIRTUAL MACHINE
(JVM)

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Java Approach

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 Java Features
• Platform Independence
• Object oriented
• Compiled and interpreted
• Robust
• Security
• Strictly typed language
• Lack of pointers
• Garbage collection
• Strict compile time checking
• Sandbox security

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 Java Features
• Multithreaded

• Dynamic binding

• Performance

• Networking

• No pointers

• No global variables

• Automatic Garbage collection

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 Java 5 New Features
• Autoboxing and unboxing
• Enhanced For loop
• Metadata
• Variable arguments
• Static import
• Graphics enhancemnets
• Generics
• Enum
• StringBuilder class

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 Java 6 New Features
• Enhancements in Collections API

• Console class

• Jar and Zip enhancements

• Enhancements to Network Interface

• Enhancements in Java web start and plug in

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 Java 7 New Features
• String in switch…case Statement

• Unicode 6.0.0 Support

• Binary Literals and Numeric Literals (with Underscores)

• Automatic Resource Management

• Improved Exception Handling

• nio 2.0 (Non-blocking I/O)—New File System API

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 Java 7 Features (contd.)
• Fork and Join for parallel processing

• Supporting Dynamism using invoke dynamic to let JVM resolve type

info at runtime

• No need of Diamond Operator <> on right side of the expression

• Swing Enhancements

• Java FX 2.2.3 provides the new GUI toolkit for creating rich cross

platform user interfaces

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Comparison of Java Versions

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 Differences between C++ and Java
• Multiple Inheritance not allowed
• Multi-level inheritance is enforced, which makes the design clearer. Multiple
inheritance among classes is not supported in java. Interfaces are used for
supporting multiple inheritance.
• Common parent
• All classes are single-rooted. The class Object is the parent of all the classes in
java.
• Packages
• The concept of packages is used, i.e. a large, hierarchical namespace is
provided. This prevents naming ambiguities in libraries.
• In-source documentation
• In-source code documentation comments are provided. Documentation
keywords are provided for example: @author, @version, etc.
• All code inside class
• All code resides inside a class. Global data declaration outside the class is not
allowed. However, static data within classes is supported.

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 Differences between C++ and Java
• Operator overloading
• Operator overloading is not supported in java but there are few
operators which are already overloaded by java, e.g. ‘+’. Programmers
do not have the option of overloading operators.
• Explicit boolean type
• boolean is an explicit type, different from int. Only two boolean literals
are provided i.e. true and false. These cannot be compared with
integers 0 and 1 as used in some other languages.
• Array length accessible
• All array objects in java have a length variable associated with them to
determine the length of the array.

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 Differences between C++ and Java
• goto
• Instead of goto, break and continue are supported.
• Pointers
• There are no pointers in java.
• null pointers reasonably caught
• Null pointers are caught by a NullPointerException.
• Memory management
• Explicit destructor is not needed. The use of garbage collection
prevents memory leaks and referencing freed memory.
• Automatic variable initialization
• Variables are automatically initialized except local variables.
• Runtime container bounds checks
• The bounds of containers (arrays, strings, etc.) are checked at runtime
and an IndexOutOfBoundsException is thrown if necessary.

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 Differences between C++ and Java
• All definitions are well defined
• Methods and fields carry explicitly one of the access modifiers.
• Sizes of the integer types defined
• The sizes of the integer type’s byte, short, int and long are defined to
be 1, 2, 4 and 8 bytes.
• Unicode provided
• Unicode represents character in most of the languages, e.g. Japanese,
Latin etc.
• String class
• An explicit predefined String class is provided along with StringBuffer
and new StringBuilder class.

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 Differences between C++ and Java
• Extended utility class libraries: package java.util

• Supported among others: Enumeration (an Iterator interface), Hashtable,

Vector.

• Multithreading support with synchronization

• Java supports multithreading with synchronization among them.

• Default access specifier added

• By default, in java all variables, methods and classes have default privileges
which are different from private access specifier. Private is the default access
specifier in C++.

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 JVM and JRE
• JVM is a part of JRE

Java Runtime Environment

Operating Systems (Windows, Unix, etc.)

Hardware (Intel, Motorola, Alpha, etc.)

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 Program Structure
• A Java Application consists of
a collection of classes.
• A class is a template
containing methods and
variables.

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 First Java Program
/* Call this file “Example.java”.*/

class Example {

//your program starts execution with a call to //main()

public static void main(String args[ ]){

System.out.println(“This is a simple Java program”);

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 Executing Java Program
• Entering the source code: text editor like notepad or any IDE
• Saving the source code:
• Select File | Save As from the notepad menu.
• In the ‘File name’ field, type “Example.java” within the double
quotes.
• In the ‘Save as type’ field select All Files (*.*).
• Click enter to save the file.
• Compiling & running the source
• type cmd at the run prompt.
• move to the folder that contains the saved Example.java file.
• compile the program using javac,
• C:\javaeg\>javac Example.java

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 Executing Java Program
• Compilation creates a file called Example.class

• This class contains bytecode which is interpreted by JVM.

• To execute the program type the following command at the dos

prompt:

• C:\javaeg\>java Example

• The output of the program is shown below:

• This is a simple Java program

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 Why save as Example.java?
• The name of the .class file will match exactly with the name of the
source file.

• That is why it is a good idea to give the Java source files the same
name as that of the class they contain.

• Java is case-sensitive.

• So example and Example are two different class names.

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 Your Turn
• Let us revise the concepts
• What is platform independence?

• What is the relation between JVM and JRE?

• Differences between C++ and Java?

• Why the source file is named after the class name in java?

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 Installation of Java
• Download the JDK installer.

• Run the JDK installer.

• Update PATH Environment variables.

• Test the installation – run javac and java on command prompt.

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Installed Directory Structure

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 Installed Directory Structure
• src.zip file contains all the core class binaries, and is used by JDK in
this form.
• include\ directory contains a set of C and C++ header files for
interacting with C and C++.
• lib\ directory contains non-core classes like dt.jar and tools.jar used
by tools and utilities in JDK.
• bin\ The bin directory contains the binary executables for Java. For
example, Java Compiler (Java), Java Interpreter (Java) , rmicompiler,
(rmic) etc.
• jre\ is the root directory for the Java runtime environment.
• db\ contains java database.

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Exploring the JDK

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 Exploring the JDK
JDK=JRE + JAVA API

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 Tools in JDK
• Basic Tools in Java

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 IDE
• Tools specifically designed for writing Java code.

• Tools offer a GUI environment to compile and debug your Java

program easily from the editor environment, as well as browse
through your classes etc.

• Popular IDEs

• Eclipse

• Netbeans

• Kawa

• JCreator
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 Summary
• Java is an object-oriented language.
• Java is designed to be platform independent, so it can run on multiple
platforms.
• Every Java program consists of one or more classes.
• A class is nothing but a template for creating objects.
• In Java, code resides inside a class.
• Java bytecode executes on a special type of microprocessor.
• As there was not a hardware implementation of this microprocessor
available when Java was first released, the complete processor
architecture was emulated by a software known as virtual machine.
(popularly known as JVM).

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