Aim:
Write a program in (Eclipse) Java
to display String “Hello World”
Theory:
Java is a general-purpose computer programming language that is concurrent, class-based, object-oriented, and specifically designed to have as
few implementation dependencies as possible. It is intended to let application
developers "write
once, run anywhere" (WORA), meaning that compiled Java code can run on all
platforms that support Java without the need for recompilation. Java applications are typically
compiled to bytecode that can run on any Java virtual machine (JVM) regardless of
computer architecture. As of 2015, Java
is one of the most popular
programming languages in use, particularly for client-server web
applications, with a reported 9 million developers. Java was originally
developed by James Gosling at Sun Microsystems (which has since been acquired
by Oracle Corporation) and released in 1995 as a core component of Sun
Microsystems' Java
platform.
The language derives much of its syntax from C and C++, but it has fewer low-level facilities than either of
them.
Java Software Platform:
Writing in the Java programming language is the primary way to produce code
that will be deployed as byte
code in a Java Virtual Machine (JVM); byte code compilers are also available for other
languages, including Ada, JavaScript, Python, and Ruby. In addition, several languages
have been designed to run natively on the JVM, including Scala, Conjure and Groovy. Java
syntax borrows heavily from C and C++, but
object-oriented features are modeled after Smalltalk and Objective-C. Java eschews certain low-level
constructs such as pointers and has a very simple memory model
where every object is allocated on the heap and all variables of object types are references. Memory management is
handled through integrated automatic garbage collection performed by the JVM.
Java Development Kit:
The Java Development Kit (JDK) is an implementation of either one of the Java SE, Java EE or Java ME platforms released
by Oracle Corporation in the form of a binary
product aimed at Java developers on Solaris, Linux, Mac OS X or Windows. The JDK includes a private JVM and a few other resources to
finish the development of a Java Application. Since the introduction of the Java platform, it has been by
far the most widely used Software Development Kit (SDK). On 17
November 2006, Sun announced that it would be released under the GNU General Public License (GPL), thus making it free software. This happened in
large part on 8 May 2007, when Sun contributed the source code to the Open JDK.
Java Package:
A Java package is a technique for organizing Java classes into namespaces similar to the modules of Modula, providing modular programming in Java. Java packages
can be stored in compressed files called JAR files, allowing classes to be downloaded faster as
groups rather than individually. Programmers also typically use packages to
organize classes belonging to the same category or providing similar
functionality. A package provides a unique namespace for the types it contains.
Classes in the same package can access each other's package-private and
protected members.
Java Class:
A Java
class file is a file (with the .class filename extension) containing Java
bytecode that
can be executed on the Java Virtual Machine (JVM). A Java
class file is produced by a Java
compiler from Java programming language source
files (.java files) containing Java classes. If a source file has more
than one class, each class is compiled into a separate class file.
JVMs are available for many platforms, and a class file compiled
on one platform will execute on a JVM of another platform. This makes Java platform-independent.
Program:
class
HelloWorldApp {
public static void main(String[]
args) {
System.out.println("Hello
World!"); // Prints the string to the console.
}
}
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