Java Remaining

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Nimbus InfocomAura Of Excellence In Computer Education

7, Daan Bari

Jawahar Nagar

Kota (Rajasthan)Mobile No. : 09928088743

C, C++, DSA, VB, VB.Net, C#, ASP.Net, Java(Core & Adv), PHP+MySql, UNIX, LINUX, Oracle, PL/SQL, BCA, MCA, BTECH

Local Applet and Remote Applet

An Applet is a window based java program that is used for internet applications. These can berun by using either web browser or with an applet viewer. There are two types of applets: Localapplets and Remote applets.

Local AppletA LOCAL applet is the one which is stored on our computer system.when browser try to accessthe applet, it is not necessary for our computer to be connected to The Internet.

Remote appletsRemote applets are developed by unknown persons and stored in remote computers. To run a

remote applet internet connection is needed. At the run time the system searches the appletcode in the internet and it is downloaded. To download a remote applet, we must give the

address of the applet in HTML page.

Difference between JDK, JRE and JVMJDK (Java Development Kit)Java Developer Kit contains tools needed to develop the Java programs, andJREto run theprograms. The tools include compiler (javac.exe), Java application launcher (java.exe),Appletviewer, etc

Compiler converts java code into byte code. Java application launcher opens aJRE, loads the

class, and invokes its main method.

You needJDK, if at all you want to write your own programs, and to compile the m. For runningjava programs, JRE is sufficient.

JRE is targeted for execution of Java files i.e. JRE = JVM + Java Packages Classes(like util,math, lang, awt,swing etc)+runtime libraries.JDKis mainly targeted for java development. I.e. You can create a Java file (with the help ofJava packages), compile a Java file and run a java file

JRE (Java Runtime Environment)Java Runtime Environment contains JVM, class libraries, and other supporting files. It does notcontain any development tools such as compiler, debugger, etc. Actually JVM runs the program,and it uses the class libraries, and other supporting files provided in JRE. If you want to run any

java program, you need to have JRE installed in the system

TheJava Virtual Machine provides a platform-independent way of executing code;programmers can concentrate on writing software, without having to be concerned with how or

where it will run.

If u just want to run applets (ex: Online Yahoo games or puzzles),JREneeds to be installed onthe machine.

JVM (Java Virtual Machine)As we all aware when we compile aJava file, output is not an 'exe' but it's a '.class' file. '.class'

file consists ofJava byte codes which are understandable by JVM. Java Virtual Machineinterprets the byte code into the machine code depending upon the underlying operatingsystem and hardware combination. It is responsible for all the things like garbage collection,array bounds checking, etc JVM is platform dependent.

Topic : Java Page 1Notes ByNAGESH KUMAR Contact No: 09928088743
http://classof1.com/homework_answers/computer_science/html/http://classof1.com/homework_answers/computer_science/html/


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TheJVMis called "virtual" because it provides a machine interface that does not depend on theunderlying operating system and machine hardware architecture. This independence fromhardware and operating system is a cornerstone of the write-once run-anywhere value of Java

programs.

There are different JVM implementations are there. These may differ in things like performance,reliability, speed, etc. These implementations will differ in those areas where Java specification

doesnt mention how to implement the features, like how the garbage collection process worksis JVM dependent, Java spec doesnt define any specific way to do this.

Getting User InputIn Java 1.0, the only way to perform console input was to use a byte stream, and older codethat uses this approach persists. Today, using a byte stream to read console input is still

technically possible, but doing so may require the use of a deprecated method, and thisapproach is not recommended. The preferred method of reading console input for Java 2 is to

use a character-oriented stream, which makes your program easier to internationalize andmaintain.

Java does not have a generalized console input method that parallels the standard C functionscanf( ) or C++ input operators.In Java, console input is accomplished by reading from System.in. To obtain a character-basedstream that is attached to the console, you wrap System.in in a BufferedReader object, tocreate a character stream. BuffereredReader supports a buffered input stream. Its mostcommonly used constructor is shown here:

BufferedReader(Reader inputReader)

Here, inputReaderis the stream that is linked to the instance ofBufferedReader that is being

created. Reader is an abstract class. One of its concrete subclasses is InputStreamReader,which converts bytes to characters. To obtain an InputStreamReader object that is linked toSystem.in, use the following constructor:

InputStreamReader(InputStream inputStream)

Because System.in refers to an object of type InputStream, it can be used for inputStream.Putting it all together, the following line of code creates a BufferedReader that is connected to

the keyboard:

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

After this statement executes, br is a character-based stream that is linked to the consolethrough System.in.

Reading CharactersTo read a character from a BufferedReader, use read( ). The version ofread( ) that we willbe using is int read( ) throws IOException Each time that read( ) is called, it reads a characterfrom the input stream and returns it as an integer value. It returns 1 when the end of thestream is encountered. As you can see, it can throw an IOException.

The following program demonstrates read( ) by reading characters from the console until theuser types a q:

// Use a BufferedReader to read characters from the console.import java.io.*;class BRRead{

public static void main(String args[]) throws IOException{



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char c;BufferedReader br = new BufferedReader(new InputStreamReader(System.in));System.out.println("Enter characters, 'q' to quit.");

// read charactersdo

{c = (char) br.read();

System.out.println(c);} while(c != 'q');

}}Here is a sample run:Enter characters, 'q' to quit.123abcq1

23

ab

cqThis output may look a little different from what you expected, because System.in is linebuffered, by default. This means that no input is actually passed to the program until you pressENTER. As you can guess, this does not make read( ) particularly valuable for interactive,console input.

Reading Strings

To read a string from the keyboard, use the version ofreadLine( ) that is a member of theBufferedReader class. Its general form is shown here:

String readLine( ) throws IOException

It returns a String object.The following program demonstrates BufferedReader and the readLine( ) method; theprogram reads and displays lines of text until you enter the word stop:

// Read a string from console using a BufferedReader.import java.io.*;class BRReadLines

{ public static void main(String args[]) throws IOException{

// create a BufferedReader using System.inBufferedReader br = new BufferedReader(new InputStreamReader(System.in));String str;System.out.println("Enter lines of text.");System.out.println("Enter 'stop' to quit.");do{

str = br.readLine();

System.out.println(str);}

while(!str.equals("stop"));}

}



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Comparison of Java and C++The differences between the C++ and Java programming languages can be traced to theirheritage, as they

have different design goals.

C++ was designed mainly for systems programming, extending the C programming language. To this

procedural programming language designed for efficient execution, C++ has added support for

statically-typedobject-oriented programming,exception handling,scoped resource management, and

generic programming, in particular. It also added a standard librarywhich includes generic containers

and algorithms.

Java was created initially to support network computing. It relies on a virtual machine to be secure

and highlyportable. It is bundled with an extensive library designed to provide a complete abstraction

of the underlying platform. Java is a statically-typed object-oriented language that uses a syntax

similar to C++, but is not compatible with it. It was designed from scratch, with the goal of being easy

to use and accessible to a wider audience.

The different goals in the development of C++ and Java resulted in different principles and design trade-offs

between the languages. The differences are as follows:

C++ Java

Compatible with Csource code, except for a few

corner cases.

No backward compatibility with any previous

language. The syntax is however strongly influenced

by C/C++.

Write once compile anywhere (WOCA)Write once run anywhere / everywhere (WORA /

WORE)

Allowsprocedural programming,object-oriented

programming, and generic programming.

Encourages an object orientedprogramming paradigm.

Allows direct calls to native system libraries.Call through theJava Native Interface and recently

Java Native Access

Exposes low-level system facilities. Runs in a protected virtual machine.

Only provides object types and type names.Is reflective, allowing metaprogramming and dynamic

code generation at runtime.

Has multiple binary compatibility standards

(commonly Microsoft and Itanium/GNU)

Has a binary compatibility standard, allowing runtime

check of correctness of libraries.

Optional automatedbounds checking. (e.g. the at()

method in vector and string containers)

Normally performs bounds checking.HotSpot can

remove bounds checking.

Supports native unsigned arithmetic. No native support for unsigned arithmetic.

Standardized minimum limits for all numerical types,but the actual sizes are implementation-defined.

Standardized types are available as typedefs

(uint8_t, ..., uintptr_t).

Standardized limits and sizes of all primitive types on

all platforms.

Pointers, References, and pass by value are supportedPrimitive and reference data types always passed by

value.

Explicit memory management, though third party

frameworks exist to provide garbage collection.

Supports destructors.

Automatic garbage collection (can be triggered

manually). Doesn't have the concept ofDestructorand

usage offinalize() is not recommended.

Supports class, struct, and union and can allocate them

onheaporstack

Supports only class and allocates them on the heap.

Java SE 6 optimizes with escape analysis to allocate

some objects on the stack.Allows explicitly overriding types.

Rigidtype safetyexcept for widening conversions.

Autoboxing/Unboxing added in Java 1.5.

TheC++ Standard Library has a much more limited The standard library has grown with each release. By

http://en.wikipedia.org/wiki/Virtual_Heritagehttp://en.wikipedia.org/wiki/Virtual_Heritagehttp://en.wikipedia.org/wiki/C_(programming_language)http://en.wikipedia.org/wiki/Procedural_programminghttp://en.wikipedia.org/wiki/Static_typinghttp://en.wikipedia.org/wiki/Object-oriented_programminghttp://en.wikipedia.org/wiki/Object-oriented_programminghttp://en.wikipedia.org/wiki/Exception_handlinghttp://en.wikipedia.org/wiki/Exception_handlinghttp://en.wikipedia.org/wiki/Exception_handlinghttp://en.wikipedia.org/wiki/RAIIhttp://en.wikipedia.org/wiki/RAIIhttp://en.wikipedia.org/wiki/Generic_programminghttp://en.wikipedia.org/wiki/C%2B%2B_Standard_Libraryhttp://en.wikipedia.org/wiki/C%2B%2B_Standard_Libraryhttp://en.wikipedia.org/wiki/Network_computinghttp://en.wikipedia.org/wiki/Virtual_machinehttp://en.wikipedia.org/wiki/Computer_securityhttp://en.wikipedia.org/wiki/Portinghttp://en.wikipedia.org/wiki/Portinghttp://en.wikipedia.org/wiki/C_(programming_language)http://en.wikipedia.org/wiki/C_(programming_language)http://en.wikipedia.org/wiki/Corner_casehttp://en.wikipedia.org/wiki/Procedural_programminghttp://en.wikipedia.org/wiki/Procedural_programminghttp://en.wikipedia.org/wiki/Object-oriented_programminghttp://en.wikipedia.org/wiki/Object-oriented_programminghttp://en.wikipedia.org/wiki/Object-oriented_programminghttp://en.wikipedia.org/wiki/Generic_programminghttp://en.wikipedia.org/wiki/Programming_paradigmhttp://en.wikipedia.org/wiki/Java_Native_Interfacehttp://en.wikipedia.org/wiki/Java_Native_Interfacehttp://en.wikipedia.org/wiki/Java_Native_Accesshttp://en.wikipedia.org/wiki/Reflection_(computer_science)http://en.wikipedia.org/wiki/Reflection_(computer_science)http://en.wikipedia.org/wiki/Bounds_checkinghttp://en.wikipedia.org/wiki/Bounds_checkinghttp://en.wikipedia.org/wiki/HotSpothttp://en.wikipedia.org/wiki/HotSpothttp://en.wikipedia.org/wiki/Destructor_(computer_science)http://en.wikipedia.org/wiki/Destructor_(computer_science)http://en.wikipedia.org/wiki/Dynamic_memory_allocationhttp://en.wikipedia.org/wiki/Dynamic_memory_allocationhttp://en.wikipedia.org/wiki/Dynamic_memory_allocationhttp://en.wikipedia.org/wiki/Stack-based_memory_allocationhttp://en.wikipedia.org/wiki/Dynamic_memory_allocationhttp://en.wikipedia.org/wiki/Java_version_history#Java_SE_6_Update_14http://en.wikipedia.org/wiki/Escape_analysishttp://en.wikipedia.org/wiki/Stack-based_memory_allocationhttp://en.wikipedia.org/wiki/Type_safetyhttp://en.wikipedia.org/wiki/Type_safetyhttp://en.wikipedia.org/wiki/Type_safetyhttp://en.wikipedia.org/wiki/C%2B%2B_Standard_Libraryhttp://en.wikipedia.org/wiki/C%2B%2B_Standard_Libraryhttp://en.wikipedia.org/wiki/Virtual_Heritagehttp://en.wikipedia.org/wiki/C_(programming_language)http://en.wikipedia.org/wiki/Procedural_programminghttp://en.wikipedia.org/wiki/Static_typinghttp://en.wikipedia.org/wiki/Object-oriented_programminghttp://en.wikipedia.org/wiki/Exception_handlinghttp://en.wikipedia.org/wiki/RAIIhttp://en.wikipedia.org/wiki/Generic_programminghttp://en.wikipedia.org/wiki/C%2B%2B_Standard_Libraryhttp://en.wikipedia.org/wiki/Network_computinghttp://en.wikipedia.org/wiki/Virtual_machinehttp://en.wikipedia.org/wiki/Computer_securityhttp://en.wikipedia.org/wiki/Portinghttp://en.wikipedia.org/wiki/C_(programming_language)http://en.wikipedia.org/wiki/Corner_casehttp://en.wikipedia.org/wiki/Procedural_programminghttp://en.wikipedia.org/wiki/Object-oriented_programminghttp://en.wikipedia.org/wiki/Object-oriented_programminghttp://en.wikipedia.org/wiki/Generic_programminghttp://en.wikipedia.org/wiki/Programming_paradigmhttp://en.wikipedia.org/wiki/Java_Native_Interfacehttp://en.wikipedia.org/wiki/Java_Native_Accesshttp://en.wikipedia.org/wiki/Reflection_(computer_science)http://en.wikipedia.org/wiki/Bounds_checkinghttp://en.wikipedia.org/wiki/HotSpothttp://en.wikipedia.org/wiki/Destructor_(computer_science)http://en.wikipedia.org/wiki/Dynamic_memory_allocationhttp://en.wikipedia.org/wiki/Stack-based_memory_allocationhttp://en.wikipedia.org/wiki/Dynamic_memory_allocationhttp://en.wikipedia.org/wiki/Java_version_history#Java_SE_6_Update_14http://en.wikipedia.org/wiki/Escape_analysishttp://en.wikipedia.org/wiki/Stack-based_memory_allocationhttp://en.wikipedia.org/wiki/Type_safetyhttp://en.wikipedia.org/wiki/C%2B%2B_Standard_Library


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scope and functionality than the Java standard library

but includes: Language support, Diagnostics, General

Utilities, Strings, Locales, Containers, Algorithms,Iterators, Numerics, Input/Output and Standard C

Library. The Boost library offers much more

functionality including threads and network I/O. Users

must choose from a plethora of (mostly mutually

incompatible) third-party libraries for GUI and other

functionality.

version 1.6 the library included support for locales,

logging, containers and iterators, algorithms, GUI

programming (but not using the system GUI), graphics,

multi-threading, networking, platform security,introspection, dynamic class loading, blocking and

non-blocking I/O, and provided interfaces or support

classes forXML, XSLT, MIDI, database connectivity,

naming services (e.g.LDAP), cryptography, security

services (e.g. Kerberos), print services, and web

services. SWT offers an abstraction for platform

specific GUIs.

Operator overloadingfor most operators

The meaning of operators is generally immutable,

however the + and += operators have been overloaded

for Strings.

Full multiple inheritance, including virtual inheritance. Single inheritance only from classes, multiple frominterfaces.

Compile time Templates

Genericsare used to achieve an analogous effect to C+

+ templates, however they do not translate from source

code to byte code due to the use ofType Erasure by the

compiler.

Function pointers, function objects, lambdas (in C+

+0x) and interfaces

No function pointer mechanism. Instead idioms such as

Interfaces, Adapters and Listeners are extensively used.

No standard inline documentation mechanism. 3rd

party software (e.g. Doxygen) exists.Javadoc standard documentation

const keyword for defining immutable variables and

member functions that do not change the object.

final provides a limited version ofconst,

equivalent to type* const pointers for objects andplain const of primitive types only. No const

member functions, nor any equivalent to const type*

pointers.

Supports the goto statement. Supports labels with loops and statement blocks.

Source code can be written to be platform independent

(can be compiled forWindows,BSD,Linux, Mac OS

X, Solaris etc. without needing modification) and

written to take advantage of platform specific features.

Is typically compiled into native machine code.

Is compiled into byte code for theJVM. Is dependent

on the Java platform but the source code is typically

written not to be dependent on operating system

specific features.

C++ is a powerful language designed for system programming. The Java language was designed to be simpleand easy to learn with a powerful cross-platform library. The Javastandard library is considerably large for a

standard library. However, Java does not always provide full access to the features and performance of the

platform on which the software runs. The C++ standard libraries are simple and robust providing containers

and associative arrays.

Java as an Internet LanguageJava is an object oriented language and a very simple language. Because it has no space for

complexities. At the initial stages of its development it was called as OAK. OAK wasdesigned for handling set up boxes and devices. But later new features were added to itand it was renamed as Java. Java became a general purpose language that had manyfeatures to support it as the internet language. Few of the features that favors it to be an

internet language are:

http://en.wikipedia.org/wiki/XMLhttp://en.wikipedia.org/wiki/XSLThttp://en.wikipedia.org/wiki/MIDIhttp://en.wikipedia.org/wiki/LDAPhttp://en.wikipedia.org/wiki/LDAPhttp://en.wikipedia.org/wiki/Kerberos_(protocol)http://en.wikipedia.org/wiki/Operator_overloadinghttp://en.wikipedia.org/wiki/Operator_overloadinghttp://en.wikipedia.org/wiki/Generics_in_Javahttp://en.wikipedia.org/wiki/Generics_in_Javahttp://en.wikipedia.org/wiki/Type_erasurehttp://en.wikipedia.org/wiki/Doxygenhttp://en.wikipedia.org/wiki/Javadochttp://en.wikipedia.org/wiki/Windowshttp://en.wikipedia.org/wiki/BSDhttp://en.wikipedia.org/wiki/BSDhttp://en.wikipedia.org/wiki/Linuxhttp://en.wikipedia.org/wiki/Linuxhttp://en.wikipedia.org/wiki/Mac_OS_Xhttp://en.wikipedia.org/wiki/Mac_OS_Xhttp://en.wikipedia.org/wiki/Solaris_(operating_system)http://en.wikipedia.org/wiki/JVMhttp://en.wikipedia.org/wiki/JVMhttp://en.wikipedia.org/wiki/JVMhttp://en.wikipedia.org/wiki/Operating_systemhttp://en.wikipedia.org/wiki/Standard_libraryhttp://en.wikipedia.org/wiki/Standard_libraryhttp://en.wikipedia.org/wiki/Container_(data_structure)http://en.wikipedia.org/wiki/Associative_arrayshttp://en.wikipedia.org/wiki/XMLhttp://en.wikipedia.org/wiki/XSLThttp://en.wikipedia.org/wiki/MIDIhttp://en.wikipedia.org/wiki/LDAPhttp://en.wikipedia.org/wiki/Kerberos_(protocol)http://en.wikipedia.org/wiki/Operator_overloadinghttp://en.wikipedia.org/wiki/Generics_in_Javahttp://en.wikipedia.org/wiki/Type_erasurehttp://en.wikipedia.org/wiki/Doxygenhttp://en.wikipedia.org/wiki/Javadochttp://en.wikipedia.org/wiki/Windowshttp://en.wikipedia.org/wiki/BSDhttp://en.wikipedia.org/wiki/Linuxhttp://en.wikipedia.org/wiki/Mac_OS_Xhttp://en.wikipedia.org/wiki/Mac_OS_Xhttp://en.wikipedia.org/wiki/Solaris_(operating_system)http://en.wikipedia.org/wiki/JVMhttp://en.wikipedia.org/wiki/Operating_systemhttp://en.wikipedia.org/wiki/Standard_libraryhttp://en.wikipedia.org/wiki/Container_(data_structure)http://en.wikipedia.org/wiki/Associative_arrays


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Cross Platform Compatibility: The java source files (java files with .java extension) after

compilation generates the bytecode (the files with .class extension) which is further converted

into the machine code by the interpreter. The byte code once generated can execute on any

machine having a JVM. Every operating system has it's unique Java Virtual Machine (JVM) and

the Java Runtime Environment (JRE).

Support to Internet Protocols: Java has a rich variety of classes that abstracts the Internet

protocols like HTTP , FTP, IP, TCP-IP, SMTP, DNS etc .

Support to HTML: Most of the programming languages that are used for web application uses

the html pages as a view to interact with the user. Java programming language provide it's

support to html. For example. Recently the extension packagejipxhtml is developed in java to

parse and create the html 4.0 documents.

Support to Java Reflection APIs: To map the functionalities, Java Reflection APIs provides

the mechanism to retrieve the values from respective fields and accordingly creates the java

objects. These objects enables to invoke methods to achieve the desired functionality.

Support to XML parsing: Java has JAXP-APIs to read the xml data and create the xmldocument using different xml parsers like DOM and SAX. These APIs provides mechanism to

share data among different applications over the internet.

Support to Web Services : Java has a rich variety of APIs to use xml technology in diverse

applications that supports N-Tiered Enterprise applications over the internet. Features like JAXB

, JAXM, JAX-RPC , JAXR etc enables to implement web services in java applications. It makes

java a most suited internet language.

Support to java enabled Mobile devices: Java programming language is made in such a way

so that it is compatible with mobile devices also. Java language also works with any java

enabled mobile devices that support MIDP 1.0/2.0 including the symbian OS mobile devices.

Support to Personal Digital Assistants: Java language is compatible with Personal Java 1.1

such as chaiVM, Jeode, CrEME, and JV-Lite2 or with all the later version and it also support

PDAs like HP/Compaq, iPAQ, Fujitsu-Siemens Pocket Loox and SimPad, HHP, NEC, Samsung,

Sharp Electronics, Toshiba, psion m5, and any other device with Windows CE/Pocket PC

2002/2003/2005).


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