What is Java?
Java is one of the most popular programming languages in the world. Java may be used to build various types of applications such as desktop, web, mobile apps, games, and distributed systems. It’s a full-fledged programming language for creating applications.
James Gosling of Sun Microsystems developed Java. Originally known as “Oak,” it was a platform-independent language for programming home appliances before being renamed “Java” in 1995. Java is now owned by Oracle.
Java is a free and open-source programming language. It’s safe, quick, and powerful. Java is an object-oriented programming language that gives programs a logical structure and allows code to be reused. But Java is not a pure object-oriented programming language because it supports primitive data types and does not treat everything as an object.
Java Development Kit
To create Java applications, we need the Java Development Kit (JDK). The Java Development Kit (JDK) includes a compiler, the Java Runtime Environment (JRE), and a library of classes for building applications.
Java Editions
There are four different editions of Java, each of which is used to create a different type of application:
Java Standard Edition (SE) is the core Java platform. It includes all of the libraries that every Java developer should be familiar with.
Java Enterprise Edition (EE) is used for building very large-scale,
distributed systems. It’s based on Java SE and includes libraries for developing fault-tolerant, distributed multi-tier software.
Java Micro Edition (ME) is a mobile-friendly subset of Java SE. It also includes mobile-specific libraries.
Java Card is used in smart cards.
How Java Code Gets Executed?
The Java compiler converts Java code to Java Bytecode, which is a platform-independent format. The Java Virtual Machine (JVM) is loaded into memory when we launch Java programs. It takes our bytecode as input and converts it to native code for the operating system underneath.
In Java, even the simplest program needs to be written using a class. Java programs begin executing at method main. The main method must be specified as described above. The class’s name is HelloWorld. A public class must be saved in a file with the same name as the class. i.e. HelloWorld.java is the name of the file where the above code should be saved.
Java Program Patterns
Stand-Alone Applications :
- Java programs that run in the command console
- Applications with GUI (awt/swing)
Web-based Java Applications :
- Programs that run inside request/response-oriented servers
- An extension to the servlet architecture. Allow for the
separation of the display of web content and the generation
of that content - Servlets, JavaServer Pages