Java history, versions, types of errors and exception, quiz

JAVA
BASIC TERMS TO BE KNOWN…..

Facts and history
Who invented java?
James Gosling
Where?
Sun lab also known as sun micro
system.
When?
Around 1992, published in 1995.
What is first name at a time of invention?
“oak”, from the name of tree outside
the window of James.

Facts and history
Why the name “java” and the symbol a “coffee cup”?
Some issues with the name “oak”.
Seating in the local café.
Wounded up with the name “java”.
From the cup of coffee.
What is the relation with c/c++?
Java was created as a successor to C++ in order
to address various problems of that language

Features of java
Compiled and interpreted
 Source code  byte code and byte code  machine code
 Platform independent and portable
 Can be run on any platform
 Secure
 Ensures that no virus is communicated with applet
 Distributed
 Multiple programmers at different remote locations can collaborate and work together
 High performance
 Faster execution speed
 Multi language supported
Dynamic and extensible
New class library, classes and methods can be linked dynamically

JIT, Jvm, jre and jdk
 JIT
 Just-In-Time
 Component of JRE
 Improves the performance
 JVM
 Provides runtime environment in which java byte
code is executed.
 Compilation + interpretation
 Not physically present
 JRE
 Runtime environment
 Implementation of JVM
 Contains a libraries + other files
 JDK
 JRE + development tools
 Bundle of softwares

Different versions
 JDK 1.0 (January 21, 1996)
 JDK 1.1 (February 19, 1997)
 J2SE 1.2 (December 8, 1998)
 J2SE 1.3 (May 8, 2000)
 J2SE 1.4 (February 6, 2002)
 J2SE 5.0 (September 30, 2004)
 Java SE 6 (December 11, 2006)
 Java SE 7 (July 28, 2011)
 Java SE 8 (March 18, 2014)

Advantages over c/c++
 Improved software maintainability
 Faster development
 Lower cost of development
 Higher quality software
 Use of notepad makes it easier
 Supports method overloading and overriding
 Errors can be handled with the use of Exception
 Automatic garbage collection

STARTING THE BASICS…
File name: Abc.java
Code:
class abc
{
public static void main(String args[])
{
System.out.print("hello, how are you all??");
}
}

Meaning of each term
Public: visibility mode
Static: to use without creating object
Void: return type
String: pre-defined class
Args: array name
System: pre-defined class
Out: object
Print: method
Make sure:
 No need of saving file with initial capital
letter
 File name can be saved with the different
name of class name

String to integer and double
class conv
{
public static void main(String a[])
{
int a;
String b="1921";
double c;
a=Integer.parseInt(b);
System.out.println(a);
c=Double.parseDouble(b);
System.out.println(c);
}
}

Final variable
Value that will be constant through out the program.
 Can not assign another value.
 Study following program.
class fin
{
public static void main(String a[])
{
final int a=9974;
System.out.print(a);
a=759;
System.out.print(a);
}
}

Errors and exception
What is the difference???
Errors
Something that make a program go wrong.
 Can give unexpected result.
Types:
Compile-time errors
 Run-time errors
Exception
 Condition that is caused by a run-rime error in the program.
 Ex. Dividing by zero.
 Interpreter creates an exception object and throws it.

errors
Compile-time Error
 Occurs at the time of compilation.
 Syntax errors
 Detected and displayed by the interpreter.
 .class file will not be created
 For successful compilation it need to be fixed.
 For ex. Missing semicolon or missing brackets.

More examples
 Misspelling of identifier or keyword
 Missing double quotes in string
 Use of undeclared variable
 Use of = in place of == operator
 Path not found
Changing the value of variable which is declared final

errors
Run-time Error
 Program compile successfully
 Class file also generated.
 Though may not run successfully
 Or may produce wrong o/p due to wrong logic
 Error message generated
 Program aborted
 For ex. Divide by zero.

More examples
 Accessing an element that is out of bound of an array.
Trying to store a value into an array of an incompatible class or type.
 Passing a parameter that is not in a valid range.
 Attempting to use a negative size for an array.
 Converting invalid string to a number
 Accessing a character that is out of bound of a string.

class Err
{
public static void main(String bdnfs[])
{
int a=50,b=10,c=10;
int result=a/(b-c);
System.out.print(result);
int res=a/(b+c);
System.out.print(res);
}
}
WHICH ONE IS THIS??

exception
 Caused by run-time error in the program.
 If it is not caught and handled properly, the interpreter will display an error message.
 Ex. ArithmeticException
ArrayIndexOutOfBoundException
FileNotFoundException
OutOfMemoryExcepion
SecurityException
StackOverFlowException

Exception HANDLING
 In previous program , if we want to continue the execution with the remaining
code, then we should try to catch the exception object thrown by error condition
and then display an appropriate message for taking correct actions.
 This task Is known as Exception Handling.
 The purpose of this is to provide a means to detect and report circumstances.
 So appropriate action can be taken
 It contains 4 sub tasks.
 Find the problem(Hit)
 Inform that error has occurred(Throw)
 Receive the error Information(Catch)
Take corrective action(Handle)

Syntax
………………………….
………………………….
Try
{
statements; // generates an Exception
}
Catch (Exception-type e)
{
statements; // processes the Exception
}
………………………....
…………………………

example
class Err2
{
{
int a=50,b=10,c=10;
int result,res;
try
{
result=a/(b-c);
}
catch (ArithmeticException e)
{
System.out.println("can not divided by zero ");
}
res=a/(b+c);
System.out.print(res);
}
}

Multiple catch statements
………………………….
………………………….
Try
{
statements; // generates an Exception
}
Catch (Exception-type-1 e)
{
statements; // processes the Exception type 1
}
Catch (Exception-type-2 e)
{
statements; // processes the Exception type 2
}
.
.
.
.
Catch (Exception-type-N e)
{
statements; // processes the Exception type N
}
………………………....
…………………………

Finally statement
 Finally statement is supported by Java to handle a type of exception
that is not handled by catch statement.
 It may be immediately added after try block or after the last catch
block.
 Guaranteed to execute whether the exception Is thrown or not.
 Can be used for performing certain house-keeping operation such a
closing files and realizing system resources.
 Syntax for using finally statement is shown in next slide.

Syntax
Try
{
…………..
…………..
}
Catch (……….)
{
…………..
…………..
}
Finally
{
…………..
…………..
}
Decide according to
program that
whether to use catch
block or not…

class Err3
{
{
int a[]={50,100};
int x=5;
try
{
int p=a[2]/(x-a[0]);
}
finally
{
int q=a[1]/a[0];
System.out.println(q);
}
}
}
example

Some puzzles..
String mesg = “Answer is “; int sum = 1 + 2; System.out.println(mesg + sum);
 Output: “Answer is 3”
int sum = 5; sum = sum + sum *5/2; System.out.println(sum);
 Output: 17
int limit = 25; int count = 30; int total = 200; count *=5; limit -=5; total +=count
+ limit; System.out.println("total =" + total);
 Output: 370
String str1 = "Java"; String str2 = "Java program"; String str3 = "program";
char c = ' '; String s1 = str1 + str3; String s2 = str1 + "c"; String s3 = str1 + c;
String s4 = “ “; s4 += str1; String s5 = s4 + str3;
 Output: “Javac”

References
 http://darwinsys.com/java/javaTopTen.html
 http://www.funtrivia.com/en/subtopics/javao-programming-204270.html
 http://cs-fundamentals.com/java-programming/difference-between-jdk-jre-jvm-jit.
php
 http://www.javabeat.net/what-is-the-difference-between-jrejvm-and-jdk/
 http://www.fixoncloud.com/Home/LoginValidate/OneProblemComplete_Detailed.p
hp?problemid=535

Prepred by:
Saurabh Prajapati(11ce21)

Java history, versions, types of errors and exception, quiz

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