The Java Virtual Machine (JVM) acts as a mediator between operating systems and the Java programming language. When Java code is compiled, it produces bytecode that can run on any system with a JVM. The JVM interprets and executes the bytecode, generating output for the underlying operating system. Classes in Java contain fields to store data and methods to operate on that data. Objects are instances of classes created using the new operator, and constructors initialize objects when they are created. Exception handling uses try/catch blocks, where exceptions thrown in the try block can be caught and handled in catch blocks.

1. Java Virtual Machine
(JVM)
By:
Prof. Ansari Aadil S.
1
Prof. Aadil Ansari

2. Basic Introduction to JVM
• Java Virtual Machine is a set of software & program
components. As name suggests, it is a virtual computer
that resides within real computer.
• Java can achieve platform independent feature due to
JVM.
• When we want to write java program, we write the
source code into notepad & store it in the file having
extension .java
Prof. Aadil Ansari

3. Continue..
• The .java file is compiled using javac compiler. On
compilation a .class file gets generated. This class file is
actually a byte code.
• JVM takes byte code as an input, reads it, interprets it &
then execute it.
• JVM can generate output corresponding to the
underlying operating system.
Prof. Aadil Ansari

4. JVM act as an Mediator between OS & Java
Text Editor
Java Source
Code
javac
Byte code(.class File)
Windows Mac Linux
Run using java
Compile using javac
Java Virtual
Machine
Prof. Aadil Ansari

5. Prof. Aadil Ansari

6. Data types
Prof. Aadil Ansari

7. Prof. Aadil Ansari

8. Prof. Aadil Ansari

9. • System.out.print(“Hello”);
• System.out.print(“n”);
• System.out.print(“Java!”);
print( )method //print and wait
println( )method //print a line and move to the next line
• System.out.println(“Hello”);
• System.out.println(“Java!”);
Prof. Aadil Ansari

10. Classes
• A class is a collection of fields (data) and methods
(procedure or function) that operate on that data.
• The basic syntax for a class definition:
• For Example:-
class Rectangle {
// my Rectangle class
}
class classname [extends SuperClassName]
{
[fields declaration]
[methods declaration]
}
Prof. Aadil Ansari

11. Adding Variables: Class Rectangle with fields
• Add variables
• The fields (data) are also called the instance variables.
class Rectangle
{
int length; // Data fields OR instance Variables
float width;
}
Prof. Aadil Ansari

12. Adding Methods
• Methods are declared inside the body of the
class but immediately after the declaration of
instance variable.
• The general form of a method declaration is:
type methodname (parameter-list)
{
Method-body;
}
Prof. Aadil Ansari

13. Adding Methods to Class Rectangle
class Rectangle
{
int length;
float width;
void getData(int x, float y) //Method declaration
{
length =x;
width= y;
}
}
Method Body
Prof. Aadil Ansari

14. Constructor
• Constructor is a special method with same name
as it’s class name
• No return type for constructor. Not even void
• Constructors are implicitly called when objects
are created
• A constructor without input parameter is default
constructor
• Constructor can be overloaded
Prof. Aadil Ansari

15. class Student4
• {
int id;
String name;
Student4(int i,String n) //constructor
{
id = i;
name = n;
}
void display()
{
System.out.println(id+" "+name);
}
public static void main(String args[])
{
Student4 s1 = new Student4(111,"Karan");
Student4 s2 = new Student4(222,"Aryan");
s1.display();
s2.display();
}Prof. Aadil Ansari

16. • Output:
111 Karan 222 Aryan
Prof. Aadil Ansari

17. Creating objects of a class
• Objects in java are created using new operator.
• The new operator creates an object of specified class &
returns a reference of that object.
• For Example:- Rectangle rect1;
rect1 = new Rectangle();
Prof. Aadil Ansari

18. Continue..
 Both the statement can be combined into one as shown
below.
Rectangle rect1 = new Rectangle();
 The method Rectangle() is default constructor of class.
We can create any number of objects of Rectangle class.
Rectangle rect1 = new Rectangle();
Rectangle rect2 = new Rectangle();
Prof. Aadil Ansari

19. Prof. Aadil Ansari

20. Exception handling & Error
• Signal occurs when some unusual condition occurs.
• Various types of signals are Exceptions, Errors,
Interrupts & Controls.
• Exception:- Appropriate execution is raised when some
unusual condition occurs.
• Errors:- Compile time error.
Prof. Aadil Ansari

21. Continue
• Exception Handling:-The statements that are
likely to cause an exception are enclosed within
a try block.
• There is another block defined by keyword
catch which responsible for handling the
exception thrown by the try block.
• The catch is added immediately after the try
block.
Prof. Aadil Ansari

22. General syntax of try & catch
try
{
// exception get generated here.
}
catch(Type_of_Exception e)
{
// exception is handled here
}
Prof. Aadil Ansari

23. For Example:-
class RunErrDemo
{
public static void main(String arg[])
{
int a,b,c;
a= 10, b=0;
try
{
c = a/b; //Exception occurs because the element is
divided by 0
}
Prof. Aadil Ansari

24. Program continue..
catch(ArithmeticException e)
{
System.out.println(“You cannot divide by Zero”);
}
System.out.println(“ The value of a:” +a);
System.out.println(“The value of b:”+b);
}
}
Prof. Aadil Ansari

25. Output for above program is
You cannot divide by Zero
The value of a: 10
The value of b: 0
Prof. Aadil Ansari

26. • Any Questions???????
Prof. Aadil Ansari

27. • Thank You
Prof. Aadil Ansari