Comparison of Java with other Technologies

Programming languages are used for controlling the behavior of a machine or a computer. There are numerous Programming Languages available for the programmer to use.

Features Java C C++ PHP Dot Net
Paradigm
 OOP Procedural Procedural, OOP, Generic OO OOP
Form of Compiled Source Code
Java bytecode Executable Native Code Executable Native Code php code Executable Code
Memory management
 Managed, using a garbage
collector		 Manual Manual manual Through Encapsulation
Pointers
 No pointers Yes, very commonly used. Yes, very commonly used, but some
form of references available too. 		No pointers No pointers
Preprocessor
No Yes Yes No No
String Type
 Objects Character arrays Character arrays, objects Character Array Character Array
Complex Data Types
 Classes Structures, unions Structures, unions, classes - Structure, Enum, Classes
Inheritance
 Java does not support multiple inheritance N/A Multiple class inheritance - Not Supported
Operator Overloading
No N/A Yes Yes Yes
Goto Statement
 No Yes Yes Yes Yes
Machine Dependent
 No Yes Yes Yes No
Platform Dependent
 No Yes Yes Yes Yes

History of Java

In 1991, a small group of Sun engineers called the "Green Team" believed that the next wave in computing was the union of digital consumer devices and computers. Led by James Gosling, the team worked around the clock and created the programming language that would revolutionize our world - Java.

  • Green Project (1991) was designed for hand-held devices and set-top boxes. (Requirement was the hardware in the consumer devices was always changing but the same code use on the different hardware systems)
  • It was originally named as Oak but became unsuccessful, so in 1995, Sun changed its name to JAVA
  • James Gosling's goals were to implement a virtual machine and a language that had a familiar C/C++ style of notation. The first public implementation was Java 1.0 in 1995.
  • It promised "Write Once, Run Anywhere" (WORA).
Note : The initial version of Java is so small it fit in a floppy. Now it is of 85+MB.
Java History in Brief
Java History

JDK, JRE and JVM

  • A Java Developement Kit (JDK) is a software package which is used to develop and deploy java applications.
  • A Java RunTime Environment (JRE) is required to run Java applications interpretively on a target hardware and operating system platform.
  • A Java virtual machine (JVM) is a virtual machine that can execute Java bytecode. It is the code execution component of the Java platform.
1. JDK (Java Development Kit)
    JDK = javac compiler + .jar (libraries) + javadoc + jdb + JRE
  • JDK is a software package which is used to develop and deploy java applications.
    • JDK consists
  • javac compiler- it is use to convert .java file into .class file
  • JAR Files -are Java libraries , which contains number of classes and interfaces modularized for specific functionalities. For example, to make a database connection with database will require ojdbc.jar.
  • Javadoc - through this utility we can make Java documentaion for any java program.
  • Jdb- jdb is a java debugger.
  • JRE -Java Runtime Environment
2. JRE (Java Runtime Environment)
  • A JRE is required to run Java applications interpretively on a target hardware and operating system platform.
    • JRE = JVM (Java Virtual machine)+ jar files (libraries)

JRE
3. JVM
  • JVM is a software that is plat form specific.
  • For example for Linux platform will require a Linux based JVM , for windows platform will require a windows based JVM.
  • Now in these days JVM is bundled with Internet explorer and With other types of browsers.
Execution FLow

A JVM performs the following tasks
  • Class Loader- Load all the .class file, necessary for the execution of a program.
  • Byte code Verifier- It ensures the code does not no illegal data conversion, no stack over flow, not violate system integrity.
  • JIT(Just In time compiler)- JIT work as a cache for the JVM interpreted code. It memorized the repeated code instructions (that is interpreted by the JVM) and when JVM reqiure the same set of instructions so JIT provides these instructions to the JVM , so JVM does not interpret the same instructions again
  • Generate Native Code- The JVM and the Java API are built for every O/S platform. The Java API calls to the O/S API.