JAVA EVOLUTION

UNIT -1 CONTINUED…: 

UNIT -1 CONTINUED… 1.2 JAVA EVOLUTION INTRODUCTION JAVA HISTORY JAVA FEATURES HOW JAVA DIFFERS FROM C AND C++ JAVA AND INTERNET JAVA AND WORLD WIDE WEB WEB BROWSERS JAVA DEVELOPMENT KIT SUMMARY

INTRODUCTION: 

INTRODUCTION ORIGINALLY DEVELOPED BY JAMES GOSLING @ SUN MICRO SYSTEM. 1995-RELEASED CORE COMPONENT OF SUN MICROSYSTEMS JAVA PLATFORM. THE LANGUAGE DERIVES MUCH OF ITS SYNTAX FROM C AND C++. JAVA APPLICATION COMPLIED TO BYTECODE THAT RUN ON ANY JVM. IN MAY 2007 JAVA SUN MADE JAVA TECHNOLOGIES AS FREE SOFTWARE UNDER GENERAL PUBLIC LICENSE.

JAVA HISTORY: 

JAVA HISTORY ORIGINALLY CALLED OAK BY JAMES GOSLING MODELLED NEW LANGUAGE JAVA ON C AND C++ SUN RELEASED FIRST IMPLEMENTATION OF JAVA 1.0 IN 1995 PROVIDING WORA(WRITE ONCE READ ANYWHERE) ON POPULAR PLATFORMS DEVELOPMENT OF JAVA 1990 – SUN MICROS DECIDED TO DEVELOP SPECIAL SOFTWARE USED TO MANIPULATE CONSUMER ELECTRONIC DEVICE. 1991 – SUN MICROS DEVELOPED A NEW LANGUAGE CALLED OAK 1992 – GREEN PROJECT TEAM BY SUN DEMONSTRATED THE NEW LANGUAGE TO CONTROL LIST OF HOME APPLICATIONS

CONTINUED ……: 

CONTINUED …… 1993 – DEVELOPED WEB APPLETS USING NEW LANGUAGE THAT COULD RUN ON ANY COMPUTER CONNECTED TO INTERNET. 1994 – DEVELOPED NEW BROWSER CALLED HOTJAVA TO LOCATE AND RUN APPLET PRG ON INTERNET. 1995 – RENAMED OAK TO JAVA AND MANY BROWSER LIKE NETSCAPE AND IE SUPPORTS TO JAVA 1996 – SUN RELEASES JDK 1.0. 1997- SUN RELEASES JDK 1.1 1998 – SUN RELEASES JAVA 2 WITH VERSION OF SDK(SOFTWARE DEVELOPMENT KIT) 1999 – SUN RELEASES JAVA 2 PLATFORM ,STANDARD EDITION(J2SE) AND ENTERPRISE EDITION(I2EE) 2000 – J2SE WITH SDK 1.3 WAS RELEASED. 2002 – J2SE WITH SDK 1.4 WAS RELEASED. 2004 – J2SE WITH JDK 5.0 WAS RELEASED.IT IS KNOWN AS J2SE 5.0

JAVA FEATURES: 

JAVA FEATURES COMPILED AND INTERPRETED – JAVA COMPILER TRANSLATES SOURCE CODE TO BYTE CODE.JAVA INTERPRETER GENERATES MACHINE CODE THAT CAN BE DIRECTLY EXECUTED BY MACHINE. PLATFORM INDEPENDENT – JAVA PROGRAMS CAN BE MOVED FROM ONE COMPUTER TO ANOTHER ANYWHERE, ANYTIME . PORTABILITY – ENSURES PORTABILITY IN TWO WAYS. 1.JAVA COMPILER GENERATES BYTE CODE THAT CAN BE IMPLEMENTED ON ANY MACHINE. 2.SIZE OF PRIMITIVE DATA TYPES ARE MACHINE INDEPENDENT.

CONTINUED …..: 

CONTINUED ….. OBJECT ORIENTE D – ALL PRGM CODE AND DATA RESIDE WITHIN OBJECTS AND CLASSES. ROBUST – STRICT COMPILE TIME AND RUNTIME CHECKING FOR DATA TYPES,AUTOMATIC MEMORY ALLOCATION,GARBAGE COLLECTION ,EXCEPTION HANDLING. SECURE – ENSURE THAT VIRUSES DO NOT COMMUNICATE WITH AN APPLET,ABSENCE OF POINTERS CANNOT GAIN ACCESS TO MEMORY LOCATIONS WITHOUT PROPER AUTHORIZATION DISTRIBUTED – ENABLES MULTIPLE PROGRAMMERS @ MULTIPLE REMOTE LOCATIONS TO COLLABORATE AND WORK TOGETHER ON A SINGLE PROJECT.

CONTINUED …..: 

CONTINUED ….. SIMPLE,SMALL AND FAMILIAR – DOES NOT USE POINTERS,PREPROCESSOR,HEADER FILES,GOTO STATEMENT,OPERATOR OVERLOADING,MULTIPLE INHERITANCE.THIS MAKE SIMPLE AND SMALL.JAVA CODE LOOKS LIKE C++ MULTITHREADED AND INTERACTIVE – HANDLING MUTIPLE TASK SIMULTANEOUSLY. HIGH PERFORMANCE – USE INTERMEDIATE BYTECODE TO REDUCE OVERHEADS DURING RUNTIME. DYNAMIC AND EXTENSIBLE – PREDEFINED CLASS LIBRARIES,METHODS AND OBJECT ARE LINKED DYNAMICALLY @ RUN TIME.

CONTINUED …..: 

CONTINUED ….. SCALABILITY AND PERFORMANCE – REDUCE AMOUNT OF MEMORY USED IN JAVA RUNTIME ENVIRONMENT. ADDITIONAL FEATURES:- CORE XML SUPPORT EASE DEVELOPMENT JDBC ROWSET DESKTOP CLIENT.

HOW JAVA DIFFERS FROM C: 

HOW JAVA DIFFERS FROM C DOES NOT INCLUDE KEYWORDS SIZEOF,TYPEDEF DOES NOT CONTAIN DATA TYPES STRUCT AND UNION DOES NOT DEFINE KEYWORDS AUTO EXTERN,REGISTER, SIGNED AND UNSIGNED DOES NOT SUPPORT POINTER. DOES NOT HAVE PREPROCESSOR,WE CANNOT USE # DEFINE,#INCLUDE ETC DOES NOT SUPPORT MULTIDIMENSIONAL ARRAYS. DOES NOT USE FUNCTIONS LIKE MALLOC(),FREE() DOES NOT RETURN AN INTEGER VALUE WHILE EXECUTING TEST EXPRESSION DOES NOT INCLUDE CONST KEYWORD OR TO PASS CONST REFERNENCE EXPLICITLY ALL FUNCTIONS MUST BE METHODS

SIMILARITIES OF JAVA AND C: 

SIMILARITIES OF JAVA AND C ADDS NEW OPERATOR ADDS LABELLED, BREAK AND CONTINUE STATEMENT OPERATOR PRECEDENCE BEHAVES LIKE C NO UNSIGNED DATATYPES EXCEPT FOR CHAR IF,WHILE,FOR AND DO-WHILE – SYNTACTICALLY SAME.

HOW JAVA DIFFERS FROM C++: 

HOW JAVA DIFFERS FROM C++ DOES NOT SUPPORT OPERATOR OVERLOADING DOES NOT SUPPORT MULTIPLE INHERITANCE DOES NOT SUPPORT GLOBAL VARIABLES DOES NOT USE POINTERS REPLACE DESTRUCTOR WITH FINALIZE() FUNCTION NO HEADER FILES IN JAVA DOES NOT HAVE TEMPLATE CLASSES THUS JAVA IS SUPERSET NOR SUBSET OF C AND C++

JAVA AND INTERNET: 

JAVA AND INTERNET APPLET PROGRAMS CAN BE CREATED IN JAVA AND RUN THEM USING JAVA ENABLED BROWSER-HOTJAVA. DOWNLOAD AN APPLET LOCATED ON COMPUTER ANYWHERE IN INTERNET AND RUN ON LOCAL COMPUTER. ABILITY OF JAVA APPLETS MADE JAVE A UNIQUE PRGMMING LANGUAGE FOR INTERNET JAVA IS KNOWN AS INTERNET LANGUAGE.

JAVA AND WWW: 

JAVA AND WWW ABOUT WWW OPEN ENDED INFRM RETRIEVAL SYSTEM DESIGNED TO USE IN INTERNET DISTRIBUTED ENVIRONMENT CONTAINS WEB PAGES THAT PROVIDES INFORMATION AND CONTROLS. USES A DECISION TREE STRUCTURE TO NAVIGATE TO A NEW DOCUMENT. WEB PAGES CONTAIN HTML TAGS TO RETRIEVE , MAINPULATE AND DISPLAY DOCUMENTS. WEB BECOME MORE INTERACTIVE AND DYNAMIC WITH INCORPORATION OF JAVA INTO WEB PAGES.

CONTINUED …..: 

CONTINUED ….. JAVA INTERACTION WITH WEB USER SEND REQUEST FOR HTML DOCUMENT TO REMOTE COMPUTER’S WEB SERVER. WEB SERVER ACCEPT AND PROCESS THE REQUEST AND SEND REQUIRED DOCUMENT. HTML DOCUMENT IS RETURN TO USER BROWSER. THIS DOCUMENT CONTAIN APPLET TAG CORRESPONDING APPLET BYTECODE IS TRANFERRED TO USER’S COMPUTER. ENABLED BROWSER ON USER COMPUTER INTERPRETS BYTECODE AND PROVIDES OUTPUT.

WEB BROWSER: 

WEB BROWSER WEB BROWSER ARE USED TO NAVIGATE THROUGH INFORMATION FOUND ON NET. EXAMPLES ; HOTJAVA ,NETSCAPE NAVIGATOR,INTERNET EXPLORER. HOT JAVA :- DEVELOPED BY SUN MICROSYSTEM, DISPLAY INTERACTIVE CONTENT ON WEB , FIRST WEB BROWSER SUPPORT FOR JAVA AVAILABLE FOR WIN 95 , WIN NT,WIN XP PLATFORM

CONTINUED …..: 

CONTINUED ….. NETSCAPE NAVIGATOR : - DEVELPOED BY NETSCAPE COMMUNICATIONCORPORATION , AVAILABLE FOR WIN 95,NT,SOLARIS,APPLE MACHINETOSH, SUPPORTS JAVA SCRIPT –SCRIPTING LANGUAGE USED IN HTML DOCUMENTS. INTERNET EXPLORER : - DEVELOPED BY MICROSOFT AVAILABLE FOR WIN 95,NT,XP. USES TOOLBARS.ICONS,MENUBARS AND DIALOGBOX FOR NAVIGATION USES JUST – IN-COMPILER(JIT) TO INCREASES SPEED OF EXECUTION.

JAVA DEVELOPMENT KIT(JDK): 

JAVA DEVELOPMENT KIT(JDK) COLLECTION OF TOOLS USED FOR DEVELOPING AND RUNNING JAVA PROGRAMS. TOOLS OF JDK :- JAVAC – JAVA COMPILER JAVA – JAVA INTERPRETER APPLETVIEWER – VIEWING JAVA APPLETS JAVAH – C HEADER FILE AND STUB GENERATOR. JAVADOC –C REATING HTML DOCUMENTS JDB – JAVA DEBUGGER JAVAP – JAVA CLASS FILE DISASSEMBLER

SUMMARY: 

SUMMARY HISTORY OF JAVA SALIENT FEATURES DIFFERS FROM C AND C++ INCORPORATES WITH WEB ABOUT JDK