Java Programming Language and Java Platform
Java as software term can be understood in two ways:
– programming language
– a software platform
Java as a programming language was developed by Sun Microsystems in 1995 after five-year work. The first name of this language was Oak.
Java has the following main features:<>
– cross-platform (syntax and a set of standard tools do not depend on a particular operating system and type of computer)
– strong typed (limited number of primitive types, strong rules of type conversion)
– adapted for Internet programming.
Java is similar to C++ without operator overloading (though it does have method overloading), without multiple inheritances, and more strong rules of type conversion. It has automatic garbage collection that allows the creation of objects in dynamic storage without explicit deallocation.
The Java compiler generates an architecture-neutral object file executable on any processor supporting the Java runtime system. The object code consists of bytecode instructions designed to be both easy to interpret on any machine and easily translated into native machine code at runtime. Therefore, a special software platform is needed.
A software platform describes a software framework (including application frameworks), that allows software to run. Different implementations of software platforms provide a standard set of functions, which are implemented in different ways, according to architecture and commands of the particular machine. Java platform consists of Java Virtual Machine and of standard class libraries.
Java Virtual Machine (JVM) is a specification for software which interprets Java programs (usually stored in a “.java” file), which have been compiled into bytecodes, and usually stored in a “.class” file. Unlike some other instruction sets, the JVM’s supports object-oriented programming directly by including instructions for object method invocation (similar to the subroutine call in other instruction sets).
The JVM itself is written in C and so can be ported to run on most platforms. The Java byte-code is independent of the platform. There are also some hardware implementations of the JVM.
Conceptually, the Java platform is implemented at two levels, depending on the purpose of software applications:
– Java Platform, Standard Edition, (Java SE) – standard edition of Java platform, designed to create and run applications for individual use;
– Java Platform, Enterprise Edition, or Java EE, is API and runtime environment for developing and running enterprise software.
Technically, Java SE platform is also implemented at two levels:
– Java Runtime Environment (JRE): Java Virtual Machine with standard class libraries.
– Java Development Kit (JDK): software means for Java development. It includes Java compiler (javac), standard Java class libraries, examples, documentation, as well as (JRE); JDK can be freely downloaded from the site of Sun Microsystems Company.
Also, each new Java version extends features of previous one. Starting from JDK 1.2, versions of Java are called Java 2. A version of JDK 1.5 is called Java 5. The Java 6 version (JDK 1.6) extends standard Java libraries.
I hope that information is enough to understand Java Platform, Thanks for reading . . .]]>