Introduction to JAVA Programming

1. JAVA
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2. OBJECTIVES
 What is Java?
 Why Java?
 Java System overview and Types of programs in java
 JVM
 JDK
 Primitive Data types in java
 Expressions in java
 Control Statements
 Naming conventions
 Arrays
 For-each loop
 Type casting
 Build first basic java program
 Command Line Arguments
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3. JAVA
 Java is high level programming language
introduced by Sun Microsystems in June 1995.
 Java is an object oriented language built upon C
& C++, It derived its object oriented features
from C++.
 The Java language has undergone several
changes since JDK 1.0 (1996) and now JSE 7 is
latest.
*jdk- Java Development Kit
*JSE- Java Standard Ediiton
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4. WHY JAVA
 Object-oriented
 Platform independent
 Built-in support for multi-threading, socket
communication and memory management
 Supports Web based applications (Applet,
Servlets and JSP)
 Vast library of predefined objects and operations
 Secure
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JAVA FEATURES
 Simple and object oriented
 Look and feel of C
 Simplified object modeling
 Portability
 Java compiler generates byte codes
 Runtime systems for various platforms
 Size and behavior of basic data types defined
 Write once, run/debug anywhere

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JAVA FEATURES CONT.
 Availability
 Windows, Linux, Solaris,…
 Embedded systems
 Compiler and runtime are free
 Free IDEs: Eclipse, Netbeans
 Library
 Rich class library
 Part of the definition
 Standard GUI toolkit

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JAVA FEATURES CONT.
 Built-in model for concurrency
 Threads at the language level
 Synchronization
 Safety
 No Pointer!
 Automatic memory management – GC
 Networking
 Web Enabled

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JAVA SYSTEM OVERVIEW

9. APPLETS , SERVLETS AND APPLICATION
 An applet is designed to be embedded in a Web
page, and run by a browser.
 A servlet is designed to be run by a web server
which act as controller for we application.
 An application is a conventional standalone
program.
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WHAT IS A VIRTUAL MACHINE?
 A virtual machine (VM) is an abstract computer
architecture
 Software on top of a real hardware
 Can run the same application on different
machines where the VM is available

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JVM CONT.
 Runtime environment for Java
 Implementation NOT defined
 Runs Java .class files
 Has to conform to Sun‘s specification

12. JDK DIRECTORY STRUCTURE
(JAVA INSTALLATIONS)
Assuming the JDK software is installed at /jdk1.7.0, here are
some of the most important directories:
/jdk1.7.0Root directory of the JDK software installation.
Contains copyright, license, and README files.
./jdk1.7.0/binExecutables for all the development tools
contained in the JDK. The PATH environment variable
should contain an entry for this directory.
/jdk1.7.0/lib Files used by the development tools.
Includes tools.jar, which contains non-core classes for support
of the tools and utilities in the JDK.
/jdk1.7.0/jre Root directory of the Java runtime environment
used by the JDK development tools. The runtime environment
is an implementation of the Java platform.
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13. PRIMITIVE DATA TYPES
 Main data types are int, double, boolean,
char
 Also have byte, short, long, float
 boolean has values true and false
 Variable Declarations look like,
 double x, y;
 int count = 0;
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14. EXPRESSIONS
 Assignment statements mostly look like those in
C; you can use =, +=, *= etc.
 Arithmetic uses the familiar + - * / %
 Java also has ++ and --
 Java has boolean operators && || !
 Java has comparisons < <= == != >= >
 Java does not have pointers or pointer arithmetic
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15. CONTROL STATEMENTS
•if (x < y) smaller = x;
•if (x < y){ smaller=x;sum += x;}
else { smaller = y; sum += y; }
•while (x < y) { y = y - x; }
•do { y = y - x; } while (x < y)
•for (int i = 0; i < max; i++) sum += i;
BUT: conditions must be boolean
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16. NAMING CONVENTIONS
Java is case-sensitive; maxval, maxVal, and
MaxVal are three different names Class names
begin with a capital letter All other names begin
with a lowercase letter Subsequent words are
capitalized: theBigOne Underscores are not used
in names,
These are very strong conventions.
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17. ARRAYS IN JAVA
 Java provides a data structure, the array, which
stores a fixed-size sequential collection of elements of
the same type. An array is used to store a collection of
data.
 Declare array
 dataType[] arrayRefVar; // preferred way.
 Creating Arrays:
 You can create an array by using the new operator
with the following syntax:
 arrayRefVar = new dataType[arraySize]; The above
statement does two things:
 It creates an array using new dataType[arraySize];
 It assigns the reference of the newly created array to
the variable arrayRefVar.
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18. FOR EACH LOOP FOR ARRAYS IN JAVA
 Since JDK 1.5 introduced a new for loop known
as foreach loop or enhanced for loop, which
enables you to traverse the complete array
sequentially without using an index variable.
 Example:
 The following code displays all the elements in
the array myList:
 public class TestArray {
 public static void main(String[] args) {
 double[] myList = {1.9, 2.9, 3.4, 3.5};
 // Print all the array elements
 for (double element: myList)
 { System.out.println(element);
 } } }
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19. TYPE CASTING IN JAVA
 Assigning a value of one type to a variable of
another type is known as Type Casting.
 In Java, type casting is classified into two types,
 Widening Casting(Implicit)
 Narrowing Casting(Explicitly done)

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20. TYPE CASTING IN JAVA
 Widening or Automatic type converion
 Automatic Type casting take place when,the two
types are compatible
 the target type is larger than the source type
 Example :
 int i = 100;
 long l = i;
 Narrowing or Explicit type conversion
 When you are assigning a larger type value to a
variable of smaller type, then you need to perform
explicit type casting.
 double d = 100.04;
 long l = (long)d;
 //explicit type casting required int i = (int)l;
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21. BUILDING STANDALONE JAVA PROGRAMS
 We can use different IDEs as well
 IDEs are more complex and have visual Java
development tools, tight integration with the
compiler or application server, and may include
tools for debugging, refactoring, version control,
and so forth. Some examples below
 Eclipse
 NetBeans
 BjueJ
 Jbuilder
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22. BUILDING STANDALONE JAVA PROGRAMS
 Prepare the file First.java using an editor
 /*
 This is a simple Java program.*/
 class First
 {
 public static void main(String args[])
 {
 System.out.println("This is a simple Java program.");
 }
 }
 Invoke the compiler: javac First.java
 This creates First.class
 Run the java interpreter: java First
 println is a member function for the System.out class
 String is built in class
* File name should be First.java
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23. COMMAND LINE ARGUMENTS
 A command-line argument is the information
that directly follows the program’s name on the
command line when it is executed. To access the
command-line arguments inside a Java program
is quite easy—they are stored as strings in the
String array passed to main( ).
 class CommandLine {
 public static void main(String args[]) {
 for(int i=0; i<args.length; i++)
 System.out.println("args[" + i + "]: " +args[i]);
 }
 }
 * length returns the length of array
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24. Thank you
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