• Core
• Introduction
• Java Fundamentals
• JDK File Structure
• Development
• Operators and Assignments
• Flow Control
• Declarations and Access Modifiers
• Garbage Collector
• Oops Concepts
• Java Object Class
• Inner classes
• Java Package
• Java.lang package
• Java.io package
• Exception handling
• Multithreading
• Regular Expressions
• Enumerations
• Internationalization
• Assertions
• Collection Framework  
• Generics
• JDBC
• Features of Java 5

Internationalization (I18N)

Various countries follow various convention to represent dates & no's etc.
Our application should generate locate specific response like for India people the response should be in term of Rs(rupees) & for the U.S. people the response should be in term of dollars($) the process of design such type of web application is called Internationalization(I18N).
We can implement I18N by using the Following classes.
1)Local
2)NumberFormat
3)DateFormat

1)Local:
A local object represents a Geo-graphic Location.

Constructor:
We can create a local object by using the following constructor
1)Locale l=new Locale(String language);
2)Locale l=new Locale(String language, String Country);
Local class defines several constants to represent some standard Locales we can use These Locale Directly without creating on own.
Example:
Locale US Locale.ENGLISH
Locale.ITALITAN Locale.UK

Note :
Locale class is the final present in java.util package
It is the direct class of object it implements clonable & serializable interface.

Importance method Of Locale Class:
1) public static Locale getDefault();
2)public static Locale getDefault(Locale l);
3)public String getLanguage();
4)public String getDislpayLanguage();
5)public String getCountry();
6)public String getDisplayCountry();
7)public static String[] getISOCountries();
8)public static String[] getISOLanguage();
9)public static Locale[] getAvailableLocale();


Number Format Classes:-
Various countries follow various convention to represent number by using Number Format classes we can format a number according to a particular Locale.
Number Format class parent in java.next package & it is an abstract class.hence we can,t create NumberFormat object directly
NumberFormat nf=new Number Format(); //invalid
Creating NumberFormat object for the default Locale:-
NumberFormat classes defines the following methods for this
1)Public static NumberFormat getInstance();
2)Public static NumberFormat getCurrencyInstance();
3)Public static NumberFormat getParcentInstance();
4)Public static NumberFormat getNumberInstance();

Getting NumberFormat object for a Specific Locale:-
We have to pass the corresponding Locale object as argument to the above methods
1)Public static NumberFormat getCurrencyInstance(Locale l);
once we get NumberFormat object we can format & parse numbers by using the Following methods of NumberFormat classes.
1)public String format(lang l);
2)public String format(double d);
To format or convert
java specific NumberFormat to locale specific String Form.
3)public Number parse(String s)Throws ParseException
To convert Locale
specific string form to java Specific number form


DateFormated class:
Various countries follow various Convensions to represent date
By using dateFormat class we can format the DATE according to a particular Locale.
DateFormat class is an abstract class & parent in java.Text pair.

Getting DateFormat object for Default Locale:
DateFormat class defines The Following methods for this
1)Public static DateFormat getInstance();
2)Public static DateFormat getDateInstance();
3)Public static DateFormat getDateInstance(int Style);
DateFormat.Full
DateFormat.Full 1
DateFormat.Full 2
DateFormat.Full 3

Getting DateFormat object for Specific Locale:
1)public static DateFormat getDateInstance(int Style,Locale l);
Once we get DateFormat object we can format & pass dates by using the following methods.
1)
public String format(Date d);
To convert Java Date form to Locale specific String form.
2)
public date parse (String s)throws parseException.


Note:
Default style is medium most of the cases default Locale is US.
Default style is Medium most of the cases default Locale is US.Development:

Javac:
We can use this command to compile a single or group of java files.
Syn: Javac [options]A.java/A.java
B.java
we can use java Command to run a .class file.

Syn java[option];
Note:- we can compile a group of .java files at a time where as we can run only one .class file at a time.
Class path : classpath described the location where required .class file are available.
JVM will always locate the required .class file.

The Following are various possible ways to set the classpath.
1)Permenently by using environment variable classpath This class path will be preserved after system restart also.

2)At command prompt level by using set Command.
Set classpath=%classpath%;D:\path>
This class path will be only for that particular command prompt once command execution completes automatically classpath will be lost.

3)At command level by using cp option
java-cpD:\path>
This classpath is applicable only for this particular command. Once command execution completes automatically classpath.will be lost.

Among the above 3 ways the most commonly used approach is setting classpath or command level.
Example:
Class Test
{
public static void main(String args[])
{
System.out.println(''Classpath Demo'');
}

1)Compiler will check only one level dependency where as JVM will check all Levels of dependency

2) If any folder structure created because Of package statement it should be resolved Through import statement only & Base package Location we have to update in classpath

3) Within the classpath the order of location is very importance for the required .class file ,JVM will always search the location.Left Right in classpath.
Once JVM finds the required.file then the rest of the classpath won't to be searched.
C: D: E:



JAR FileIf several dependent files are available then it is never recommended to set each class file individually in the classpath we have to group all those.
Class file into a single I/P file and we have to make that Zip file available in the class path.This zip file is nothing but JAR file.
Example:
To develope a servlet all required .class file are available in Servlet-api.jar.We have to make this Jar file available in the classpath then only servlet will be compiled.

jar vs war vs ear
1) jar : (java archive file)
It contains a group of .class files
2) war : (web archive file)
it represent a web application which may contain servlets,JSPS,HTML,CSS.JavaScript,etc .......
3) ear : (enterprise archive file)
It represent an enterprise application which may contains Servlets,JSPS,EJBS,JNS Components etc.

Various commands
1)
To create a jar file:
jar - cvf durga.jar A.class B.class c.class *.class
2) To extract a jar File:
jar- xvf durga.jar
3)
To display of contains of a jar file:
Jar-tvf durga.jar



Note:
Whenever we are placing a jar file in the classpath compulsory name of the jar file we should include,just Location is not enough.


ShortCut way to place jar file:-


If we are placing the jar file in the following location then it is not required to set classpath explicitly bydefault it is available to JVM & Java compiler.

JDK
JRE
LIB
ext
.jar
System Properties
For every system persistence information will be maintain in the form of system properties .These may include a name, virtual machine version, user country..etc
We can get System properties by using getProperties () method of System class
We can set System Property from the command prompt by using option
Que)
JDK vs JRE vs JVM
JDK(Java Development Kit):-

To develop & run java application the required environment provided by JDK.
JRE(Java Runtime Environment):-

To run java application the required environment provided by JRE.
JDK(Java Virtual Machine):-
The machine is responsible to execute java program.

JDK=JRE+TOOLS
JRE=JVM+Libraries

Note:
On client machine we have to install JRE,where as on the developess machine to install JDK.

Difference Between Path And Classpath
We can use classpath to describe the location where required.class files are available.


If we are not setting the classpath then our program wan't be run.
Path
we can use path variable to describe the location where reguired binary executable are available .
if we are not setting path variable then java & javac commands wan't work.
If m1() return type is void,then we will get compiletimeError saying''void type not allowed here''
Various Runtime Flags
1)
-ea: To enable assertions in every non-System class.
2)
-enableassertions:- It is Exactly same as -ea
3)
-da :- To disable assertion in every non-system class.
4)
-disableassertions:- same as -da.
5)
-esa:- To enabled assertions in every system class.
6)
-enabledSystemassertions:- it is exactly same as -esa.
7)
-dsa:- To disable assertions in nevery System class.
8)
-disableSystemassertions:- it is same as -dsa.

Example:-1)
java -ea -esa -da -esa -ea -dsa

we can use these flag in together & all these flags executed from Left To Right

Example:-2)

1)java -ea:pack1.A
2)java -ea:pack1.B -ea:pack1 pack2.D
3) java -ea -da packB

Example:-3)
pack1
A.class
B.class

pack2
C.class
D.class
TO anable assertion in only A class
1)Java -ea:pack1.A
TO anable assertion in both B & D class
2)Java -ea:pack1.B -ea:pack1:pack2.D
TO enable assertion in every non-System class except B
3) Java -ea:pack1. -da:pack1.B


TO anable assertion in every class of pack1 & its sub except sub packages
4) Java -ea:pack1.


TO anable assertion in every where with in pack1 except pack2
5) Java -ea:pack1. -da:pack1,pack2
6)
Appropriate & Inappopriate use of asserting

1)
It is always Inappropriate to mix progamimg logic with assert statement because there is no execution of assert statement at runtime.