INDEX PAGE

1. Introduction to Java

2. Installation and Setup

3. Sample Program using Notepad

4. How to Compile Java Application

5. How to Run Java Application

6. Escape Sequences

7. Print vs. Println

8. Comments

9. Variables and DataTypes

10. Eclipse

11. Package

12. Naming Conventions

13. Identifier and keyword

14. Operators

15. Control Statements

16. Input and Output

17. Arrays

18. Strings

19. StringBuffer and StringBuilder

20. Introduction to OOPS(Features)

21. Classes and Object Creation

22. Access Specifiers

23. Constructors

24. Methods

25. Static Method and Static Block

26. Instance Methods

27. This keyword

28. Inner Class and Anonymous Class

29. Inheritence

30. Super keyword

31. Polymorphism

32. Static Polymorphism

33. Dynamic Polymorphism

34. Exception Handling

35. Type Casting

36. Abstract Classes

37. Interfaces

38. Wrapper Classes

39. Collection Framework

40. Streams and Files

41. Garbage Collections

42. Threads

43. Generic Types

1. Introduction to Java

// To Do

2. Installation and Setup

Step 1:- Where to download Java

http://www.oracle.com/technetwork/java/javase/downloads/jdk7-downloads-1880260.html

Step 2:- Install JDK

1) Double click the downloaded .exe file.

2) A License agreement window opens just accept the agreement.

3) Now a Custom setup window opens. Click on the Change button and select the installation folder and click on Next which will start the installation.

4) It prompts for JRE installation click on next.

5) Now the Wizard Complete window appears which indicates the installation of jdk has been completed. Click on finish button to exit the installation process.

Step 3:- Setup JDK

1. Right click on My Computer icon and click on system properties

2. Then click on advanced tab and environment variables.

3. Now select the path in System variables and click 'Edit' button and enter the variable value

(If you install Java into a different directory, you may need to change the directory)

4. Now setup the JAVA_HOME variable.

5. clicking on "New" button and give variable name as "JAVA_HOME" and variable value as your jdk installation folder

Step 4:- Check for Successful installation

Go to the command prompt and type javac and hit enter. You should get the below screen

Prevent Errors like --> 'javac' is not recognized as an internal or external command

3. Sample Program using Notepad

Here we will learn to write first Java program. As usual first Java program would be “Hello World”. But we will change it to “Hello Vidvaan!”.

If everything till now is configured properly then we can start writting first application. Open any editor and Write below code.

1. public class FirstProgramme {

2. public static void main(String args[]) {

3. System.out.println("Hello Vidvaan!");

4. }

5. }

This class contains public static and void keywords. These are predefined words in java which carries a specific meaning.

public keyword specifies the accessibility of a class. Public means it can be accessed from any where

static keyword indicates that this method can be invoked simply by using the name of the class without creating any object for that class.

void keyword specifies that this method will not return any type of data.

main() method is the main entry point of the program, to start execution. First of all JVM calls the main method of a class and start execution . JVM (Java Virtual Machine) is responsible for running java programs.

args is a string array that takes values from java command line. It's index starts from '0'. We can access values by writing args[0], args[1] etc.

println() function prints the output on the screen.

Once finished edition save the file with name “FirstProgramme.java“. Note name of the file should be same as given as it is public class. Once file saved open the command prompt and change directory where file is saved with cd command.

4. How to Compile Java Application

Fiire “JAVAC” command to compile the java code as below.

1. D:\>cd vidvaan

2. D:vidvaan>javac FirstProgramme.java

3. C:vidvaan>

As java file is compiled properly compiler must have created a class file for the java source file in same location or other depending on package declaration. As there is no package declaration in given code so .class file will be create in same folder as java file.

5. How to Run Java Application

As java file is compiled with “JAVAC” command. We can now run the application. To run above program. Fire “JAVA” command as given below.

1. C:vidvaan>java FirstProgramme

2. Hello Vidvaan

3. C:vidvaan>

6. Escape Sequences

String literals are contained in quotation marks. So how if you want to display a quotation mark inside a string literal or how if you want to break the string literal across lines which is not possible.

So you have to make use of escape sequences to represent special characters.

Below are the sequences

Sequences	Description
\t	Tab character
\n	New line character
\”	Quotation Mark
\\	Backslash Character

Consider the following statements

Example1:

System.out.println("What \"characters\" does this \\ print?");

If you execute the above statement, you would get the following output:

What "characters" does this \ print?

Example2:

System.out.println("This\nproduces 3 lines\nof output.");

If you execute it, you will get the following output:

This

produces 3 lines

of output.

7. Print vs Println

println command produces the output on the current line and then moves the cursor to the beginning of the new line.

Print command produces the output on the current line and the cursor stays in the same line

Thus the series of print statements will generate the output on the same line. Only println will print the outputs on different lines.

Example:

System.out.println(“One”);

System.out.print(“Two”);

System.out.print(“Three”);

If you execute it, you will get the following output:

One

TwoThree

8. Comments

Comments are the text that programmers include in a program to explain their code. The compiler will ignore the comments.

Single Line Comments: These comments are used for making a single line as a comment. These comments start with //. After this double slash whatever is written till the end of the line is taken as the comment. For example

//This is my single line comment

Multiline Comments: These comments are used for making multiple lines as comments. These comments starts with /* and ends with */. For example

/* This is multiline comment line 1

This is line 2 comment

This is line 3 comment*/

9. Variables and Data Types

Variables:

Variables are nothing but a memory location to store values. This memory location has a name and a data type i.e., type of data stored.

This means when you create a variable you reserve some space in the memory. Based on the data type of a variable, the operating system allocates memory and decides what can be stored in the reserved memory. Therefore, by assigning different data types to variables, you can store integers, decimals, or characters in these variables.

DataTypes:

There are two data types

1. Primitive Data types

2. Object/Reference Data types

Primitive Data Types:

There are eight primitive data types supported by Java.

byte:

Byte data type is an 8-bit signed two's complement integer.
Minimum value is -128 (-2^7)
Maximum value is 127 (inclusive)(2^7 -1)
Default value is 0
Byte data type is used to save space in large arrays, mainly in place of integers, since a byte is four times smaller than an int.
Example: byte a = 100 , byte b = -50

short:

Short data type is a 16-bit signed two's complement integer.
Minimum value is -32,768 (-2^15)
Maximum value is 32,767 (inclusive) (2^15 -1)
Short data type can also be used to save memory as byte data type. A short is 2 times smaller than an int
Default value is 0.
Example: short s = 10000, short r = -20000

int:

Int data type is a 32-bit signed two's complement integer.
Minimum value is - 2,147,483,648.(-2^31)
Maximum value is 2,147,483,647(inclusive).(2^31 -1)
Int is generally used as the default data type for integral values unless there is a concern about memory.
The default value is 0.
Example: int a = 100000, int b = -200000

long:

Long data type is a 64-bit signed two's complement integer.
Minimum value is -9,223,372,036,854,775,808.(-2^63)
Maximum value is 9,223,372,036,854,775,807 (inclusive). (2^63 -1)
This type is used when a wider range than int is needed.
Default value is 0L.
Example: long a = 100000L, int b = -200000L

float:

Float data type is a single-precision 32-bit IEEE 754 floating point.
Float is mainly used to save memory in large arrays of floating point numbers.
Default value is 0.0f.
Float data type is never used for precise values such as currency.
Example: float f1 = 234.5f

double:

double data type is a double-precision 64-bit IEEE 754 floating point.
This data type is generally used as the default data type for decimal values, generally the default choice.
Double data type should never be used for precise values such as currency.
Default value is 0.0d.
Example: double d1 = 123.4

boolean:

boolean data type represents one bit of information.
There are only two possible values: true and false.
This data type is used for simple flags that track true/false conditions.
Default value is false.
Example: boolean one = true

char:

char data type is a single 16-bit Unicode character.
Minimum value is 0.
Maximum value 65,535.
Char data type is used to store any character.
Example: char letterA ='A'

In addition to the eight primitive data types listed above, the Java programming language also provides special support for character strings via the java.lang.String class

String:

String represents a group of characters. Simplest way is to create a string and store it in a String type variable.

Ex: String s = "this is a string";

The String class is not technically a primitive data type, but considering the special support given to it by the language. You will learn more about String Class later.

Default Values

Generally speaking, the default will be zero or null, depending on the data type. The following chart summarizes the default values for the above data types.

Data Type	Default Value (for fields)
Byte	0
Short	0
Int	0
Long	0L
Float	0.0f
Double	0.0d
Char	'\u0000'
String (or any object)	null
Boolean	false

Example Program for Data Type:

public class DataTypesinJava {

public static void main(String[] args) {

String str = "vidvaan";

int age = 23;

double fee = 8000;

float sal = 5000;

char gender = 'M';

boolean status = true;

System.out.println("Your name is :" + str);

System.out.println("Your age is :" + age);

System.out.println("salary " + sal);

System.out.println("vidvaan fee :" + fee);

System.out.println("gender :" + gender);

System.out.println("Status :" + status);

}}

Object/Reference Data types:

You will learn about reference data types later

10. Eclipse

Eclipse Download:

Step 1:- Where to download Eclipse

http://www.eclipse.org/downloads/index.php11

Step 2:- Download the zip file and save it.

Step 3:- Unzip this file that you just downloaded. It creates a folder named eclipse.

Step 4:- Create a shortcut on your desktop to the eclipse.exe file

Step 5:- Double-click the shortcut to Eclipse that you just created. In the Workspace Launcher window, in the box following Workspace:, should appear something like C:\Documents and Settings\username\workspace (where username is your login on the machine). If you want, you can type in (or browse) another location for the workspace file to be created and then click OK button.

Steps to write a first java program in eclipse:

Click File > New > Java Project

The 'Create a Java Project' box will popup.

Give your Project a name. In this case I have named it 'EclipseTutorial'

Click FINISH.
You have now setup your first project which will appear in the Package Explorer window.

Before we can begin to write any code, we must first add a Package which will contain all our project files.

Make sure your new project is highlighted and click the 'New Java Package' icon.

Give your package a name relevant to your project.

Click FINISH

Now your Package has been created we need to add a Class file. Make sure the Package is highlighted by clicking it once and then click the 'New Java Class' icon.

The Create a New Java Class box will popup.
Give your Class a name and tick the public static void main(String[] args) box.

Your Class will now appear in the Workspace and you are ready to start writing code!

Here I have wrote a simple Hello World application which will print the words into the console.

To Run your Java project. Right click the 'TutorialClass.java' file in the Package Explorer window, then click Run As > Java Application

The output will now be displayed in the console.

11. Package

A package is a namespace that organizes a set of related classes and interfaces. This can be compare to different folders in your computer. You might keep HTML pages in one folder, images in another, and scripts or applications in yet another. Because software written in the Java programming language can be composed of hundreds or thousands of individual classes, it makes sense to keep things organized by placing related classes and interfaces into packages.

Syntax: package <package_name>;

12. Naming Conventions

Package: Names of packages are written in small letters.

Ex: java.awt

java.io

Class: All class names should begin with a capital letter. When you are putting several words together to form a class name capitalize first letter of each word

Ex:AllMyChildren

An Interface is also similar to a class. A class or an interface contains methods and variables.

Methods: The names of methods should begin with lowercase letters, as in the main method. When you are putting several words together to form a method name start with the lower case and capitalize the first letter of each word.

Ex: allMyChildren

Variables: Variable naming conventions are same as method conventions.

Constants: Constants represents fixed values that cannot be altered. All letters are written in uppercase and words separated by underscores.

Ex: ALL_MY_CHILDREN

13. Identifier and keyword

Identifiers:

All Java components require names. Names used for classes, variables and methods are called identifiers.

Rules:

· All identifiers must start with a letter (A to Z or a to z), currency character ($) or an underscore (_).

· After the first character identifiers can have any combination of characters.

· A key word cannot be used as an identifier.

· Identifiers are case sensitive.

· Examples of legal identifiers: age, $salary, _value, __1_value

· Examples of illegal identifiers: 123abc, -salary

Keywords:

Keywords are nothing but reserved words havin a predefined meaning. Programmers cannot use keywords as identifiers. Below are few examples of keywords

Examples:

Continue	for	new	switch
Boolean	default	if	package
Break	do	void	private
Byte	double	while	protected
Byte	else	import	public
Case	try	instanceof	return
Catch	extends	int	short
Char	final	interface	static
Class	finally	long	throw
Throws	float	native	super

14. Operators

An operator is a symbol that performs an operation.

a + b

+ is Operator

a and b are Operands

If an operator acts on single variable, it is called a unary operator. If it acts on two variables, it is called binary operator and if it acts on three variables, this it is called ternary operator.

Below are various types of operators.

Arithmetic Operators:

These operators are used to perform fundamental arithmetic operations. There are 5 arithmetic operators in java. Since these operators work on two operands at a time, these are called binary operators. Assuming the value of a as 13 and b is 5

Operator	Meaning	Example	Result
+	Addition Operator	a+b	18
-	Substraction Operator	a-b	8
*	Multiplication Operator	a*b	65
/	Division Operator	a/b	2.6
%	Modulus	a%b	3

Addition operator is also used to join two Strings.

String s1=”wel”;

String s2=”come”;

String s3 =s1+s2;//here + will join s1 and s2 and output is welcome

Example Program:

public class ArthamaticOprators {

public static void main(String[] args) {

int num1 = 2;

int num2 = 4;

// addition

int add = num1 + num2;

System.out.println("add :" + add);

// Subtraction

int sub = num1 - num2;

System.out.println("sub :" + sub);

// multification

int mul = num1 * num2;

System.out.println("mul :" + mul);

// division

int div = num1 / num2;

System.out.println("division :" + div);

// modulus

int mod = num1 % num2;

System.out.println("modulus :" + mod);

}

Unary Operators:

The unary operators require only one operand; they perform various operations such as incrementing/decrementing a value by one, negating an expression, or inverting the value of a boolean.

Operator	Meaning
+	Unary plus operator(indicates positive value)
-	Unary minus operator(negates a given value)
++	Increment Operator
--	Decrement Operator
!	Logical complement operator

Increment Operator (++):

Increment Operator is used to increment value of a variable by 1. This is denoted by the symbol “++”. This can be used in two ways.

Case1 : Appending “++” operator after the variable name

Consider the operation “i++”. Here the value of the variable “i” will be incremented by 1.

Example:

int i = 5;
i++;

Here the variable “i” will be initialized with a value 5. Then we use the increment operator to increment its value by 1. As a result, the value of the variable “i” will be incremented to 6.

Case2 : Prepending “++” operator before the variable name

Consider the operation “++i”. Here the value of the variable “i” will be incremented by 1.

Example:

int i = 5;
++i;

Here the variable “i” will be initialized with a value 5. Then we use the increment operator to increment its value by 1. As a result, the value of the variable “i” will be incremented to 6.

Difference between these two Cases

Both the cases looks similar. But there is major difference. In the first case “variable_name++” the current statement will be executed and then the value will be incremented by 1.Then the next statement will be executed.

In the second case “++variable_name” the value will be incremented by 1 first. Then the current statement will be executed.

Example1:

int value1 = 10;
int value2 = value1++;

Here we are using the increment operator, appended to the variable name (case1).

1. The value of the variable “value1” will be assigned to the variable "value2”. It means the variable “value2” gets 10 as its value.

2. Now the value of the variable “value1” will be incremented by 1. It means the value of the variable “value1” will be 11 now.

Example2:

int value1 = 10;
int value2 = ++value1;

Here we are using the increment operator, prepended to the variable name (case2).

1. At first, the value of the variable “value1” will be incremented by 1. It means the value of the variable “value1” will be 11 now.

2. The value of the variable “value1” will be assigned to the variable "value2”. It means the variable “value2” gets 11 as its value.

Decrement Operator(--):

This is used to decrement the value of a variable by 1. This is denoted by the symbol “--”.

This can be used in two ways.

Case 1- Appending “--” operator after the variable name: The current statement is executed and then decremented by 1 and then the next statement is executed.

Case 2 - Prepending “--” operator before the variable name the value will decrement the value by 1 first. Then the current statement will be executed.

Assignment Operators:

One of the most common operators is assignment operator “=”. This operator assigns a value on its right hand side to the operand on its left hand.

Ex: int x=5;

int speed = 0;

Compact Notation:

While using assignment operators some time we may have to use the same variable on both the sides of the operator. In such cases we can eliminate repetition of variable and use compact notation.

Expanded Notation	Compact Notation	Name of Operator
x=x+5	x += 10	+= is called addition assignment operator
sal=sal*10.5	sal *= 10.5	*= is called multiplication assignment operator
value = value-discount	Value -= discount	-= is called substraction assignment operator
p = p/1000	p /= 1000	/= is called division assignment operator
num = num % 5.5	num %= 5.5	%= is modulus assignment operator

Relational Operators:

Operator	Description	Example
==	Checks if the values of two operands are equal or not, if yes then condition becomes true.	(A == B) is not true.
!=	Checks if the values of two operands are equal or not, if values are not equal then condition becomes true.	(A != B) is true.
>	Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true.	(A > B) is not true.
<	Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true.	(A < B) is true.
>=	Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true.	(A >= B) is not true.
<=	Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true.	(A <= B) is true.

Example Program:

public class RelationalOperatorExample {

public static void main(String[] args) {

int value1 = 1;

int value2 = 2;

if (value1 == value2)

System.out.println("value1 == value2");

if (value1 != value2)

System.out.println("value1 != value2");

if (value1 > value2)

System.out.println("value1 > value2");

if (value1 < value2)

System.out.println("value1 < value2");

if (value1 <= value2)

System.out.println("value1 <= value2");

if (value1 >= value2)

System.out.println("value1 >= value2");

}

Logical Operators:

Below are the logical operators

Operator	Description	Example
&&	Called Logical AND operator. If both the operands are true, then the condition becomes true.	(A && B) is false.
\|\|	Called Logical OR Operator. If any of the two operands are true, then the condition becomes true.	(A \|\| B) is true.
!	Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true then Logical NOT operator will make false.	!(A && B) is true.

Conditional Operator:

Conditional operator is also known as the ternary operator. This operator consists of three operands and is used to evaluate Boolean expressions. The goal of the operator is to decide which value should be assigned to the variable.

Syntax:

variable x= (expression)?value if expression is true: value if expression is false

Example Program:

public class ConditionalOperators {

public static void main(String[] args) {

int a, b;

a = 10;

b = (a == 1) ? 20 : 30;

System.out.println("Value of b is : " + b);

b = (a == 10) ? 20 : 30;

System.out.println("Value of b is : " + b);

}

Operator Precedence:

The operators have precedenct i.e., whish operator should be evaluated first and which operator is next in performing some caluculations

If two operator of same precedence exist in same calculation then Associativity of the operators will be used to decide which operator will be executed first.

Operator Precedence Table
Operators	Precedence(High to Low)
Postfix	expr++ expr--
Unary	++expr --expr +expr -expr ~ !
Multiplicative	* / %
Additive	+ -
Shift	<< >> >>>
Relational	< > <= >= instanceof
Equality	== !=
bitwise AND	&
bitwise exclusive OR	^
bitwise inclusive OR	\|
logical AND	&&
logical OR	\|\|
Ternary	? :
Assignment	= += -= *= /= %= &= ^= \|= <<= >>= >>>=

Example of Precedence:

public class OperatorPrecedence {

public static void main(String[] args) {

int i = 40;

int j = 80;

int k = 40;

int l = i + j / k;

System.out.println("value of L :" + l);

int m = (i + j) / k;

System.out.println("Value of M:" + m);

}

Output:

value of L :42

Value of M:3

Java/ J2EE, Oracle Adf Blog

Saturday, 7 February 2015

core Java Basics

Step 3:- Setup JDK

Step 4:- Check for Successful installation

14. Operators

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