Chapter 1. Java Fundamentals

"this chapter provides a brief overview of several Java features..."

History & Philosophy

• Developed by James Gosling, et al, at Sun Microsystems in 1991.

• Initially called Oak, renamed to Java in 1995.

• Platform independent language

• Influenced by C/C++, with similar syntax.

Java's Magic: The Bytecode

To address issues of portability and security that affected other languages, the output of a Java compiler is not directly executable code. Instead it's Bytecode, a set of instructions designed to be executed by the Java Virtual Machine (JVM).

Release Schedule

Since JDK 9, the release schedule for major updates occurs approximately every 6 months. However, a lot of new features are often only experimental at time of release. For commercial development, stick to long term support (LTS) versions Java 8, 11 + others when released.

OOP

Java is an Object Orientated Language and achieves this with three main traits:

• Encapsulation - Binding code and the data it manipulates, together.

  • A Java class is the basic unit of encapsulation to achieve this.

  • Access modifiers allow classes, and their members to be public or private.

• Polymorphism - is the quality that allows one interface to access a general class of actions.

  • Polymorphism helps to reduce complexity by allowing the same interface to be used to specify

    general class of actions. This means that it's possible to design a generic interface to a group

    of related methods.

• Inheritance - The process by which one object can use the properties of another object.

  • Think class Fruit (with properties of sweetness etc), inherits properties from class Food (with properties of nutrition, edible, type etc).

  • Without this mechanism, each individual class would need to explicitly define the same properties each time.

Java Development Kit

JDK is required on the specific machine to be able to compile and run a Java program.

• There are multiple flavours of the JDK. Oracle and OpenJDK are popular.

• JDK supplies two main programs; javac which is the compiler and java, which is the standard Java interpreter.

• The JDK runs in the command-prompt environment only. To compile and run a Java program you can use the command line, however this is typically handled by the IDE now.

Java Keywords

As of Java 11, there are 61 keywords defined in the language. Along with the operators and separators these form the definition of the Java language. The following keywords cannot be used as names for variables, classes or methods.

abstract	assert	boolean	break	byte	case
catch	char	class	const	continue	default
do	double	else	enum	exports	extends
final	finally	float	for	goto	if
implements	import	instanceof	int	interface	long
module	native	new	open	opens	package
private	protected	provides	public	requires	return
short	static	strictfp	super	switch	synchronized
this	throw	throws	to	transient	transitive
try	uses	void	volatile	while	with