2.Application Development Using Java Technologies Java EE vs Java SE
Java is a programming language. It was first developed by James Gosling at Sun Microsystems, which is now a part of Oracle Corporation. It was released in 1995 as a part of Sun Microsystems' Java platform. The language has developed much of its syntax from C and C++. Java applications are usually compiled to bytecode (class file) that can run on any Java Virtual Machine (JVM). Java is currently one of the most popular programming languages being used. It has about 10 million users.
There are many types of Java programs:
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Java Applet - small program written in Java and that is downloaded from a website and executed within a web browser on a client computer.
Application - executes on a client computer. If online, it has to be downloaded before being run.
JAR file (Java ARchive) - used to package Java files together into a single file (almost exactly like a .zip file).
Servlet - runs on a web server and helps to generate web pages.
Swing application - used to build an application that has a GUI (windows, buttons, menus, etc.).
EJB - runs on a web server and is used to develop large, complex websites.
Java is commonly used to teach students how to program as a first language, yet is still also used by professionals.
Java requires that each variable be initialized. Some older languages such as C, allow variables to go uninitialized, which can cause random failures with mysterious bugs.
Java requires that each method that declares a return type, always return a value. This also prevents bugs.
Java comes with a large set of classes and methods, the Java API that can be used without having to develop as much code "from scratch".
Unlike C, Java primitive types, such as int, are always the same size in the number of bits which helps achieve cross-platform compatibility.
Java used to be thought of as being slower than C, but that's less important in recent years with computers being faster.
Java has exception-handling that requires a programmer to handle error-conditions such an Input/Output errors.
Code compiled on one Java platform can be run on other platforms that support Java without modification of either the source-code nor the byte-code. For example, this means that a person can make a Java program for a Windows computer and have it run a Linux computer or a Mac computer.
Java was developed to achieve 5 main goals.
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It should be simple, object-oriented, distributed and easy to learn.
It should be robust and secure.
It should be independent of a given computer architecture or platform.
It should be very performant.
It should be possible to write an interpreter for the language. The language should also support parallelism and use dynamic typing.
Java is object oriented. Unchanged C++ or C code will not work in Java, in most cases, though Java looks much like C and C++.Java can run on many different operating systems. This makes Java platform independent. Java does this by making the Java compiler turn code into Java bytecode instead of machine code. This means that when the program is executed, the Java Virtual Machine interprets the bytecode and translates it into machine code.
The Java platform refers to a group of software products from Sun Microsystems. The platform is used to develop and run Java programs. The platform includes the execution engine (called a Java Virtual Machine) that allows Java programs to do the same thing on different computer systems.This capability of being able to develop software on one platform and running it on other platforms is called "cross-platform capability".
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