Overview

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 was originally developed by James Gosling at Sun Microsystems and released in 1995.^[1]

Java is one of the most popular current programming languages^[2] and is often used in computer science courses.

Example

Hello World

// This program displays "Hello world!"
//
// References:
// https://introcs.cs.princeton.edu/java/11hello/HelloWorld.java.html

class Main {
    public static void main(String[] args) {
        System.out.println("Hello world!");
    }
}

Output

Hello world!

Discussion

Each code element represents:^[3]

• // begins a comment
• class hello begins the Hello World program
• { begins a block of code
• public static void main(String[] args) begins the main function
• System.out.println() calls the standard output print line function
• "Hello world!" is the literal string to be displayed
• ; ends each line of Java code
• } ends a block of code

Java IDEs

There are many free cloud-based and local IDEs available to begin coding in Java. Check with your instructor or do your own research for recommendations.

Cloud-Based IDEs

• CodeChef
• GDB Online
• Ideone
• paiza.IO
• PythonTutor
• repl.it
• TutorialsPoint

Local IDEs

• BlueJ
• jEdit
• jGRASP

References

• Wikiversity: Computer Programming