2.1 Java terminology and environment
Introduction to Java
Object Oriented Programming (OOP) language.
Java technology
As programming language.
Java architecture
Java source code
Java compiler
Java bytecode (Object code)
Java Virtual Machine (JVM)
Program written in the form of text using Java.
Used to convert source code into binary program that consists of byte code. It creates .class file.
Bytecode is a set of instructions that are machine-independent. Executed by JVM.
Is a Java runtime system. Converts the bytecode in .class file to machine language.
Key concept of Java
Platform-Independent
Object-Oriented
Distributed
Secure
Simple
Portable
Multi-threaded
As development environment.
As application environment.
Robust
Bytecode and basic data types in Java makes it compatible.
Java programs written in one environment can run on all other environments.
Early and dynamic checking during runtime eliminates situations that cause errors.
Reliable.
To design programs close to the real world.
Powerful language.
To share and access data across the net.
Easy to learn and use.
To handle many tasks simultaneously.
Highly secure programming language.
Anatomy of Java program
Comment
Reserved Word
Modifiers
Statements
Blocks
Classes
Method
Main Method
Two slashes (//) in a line, or enclosed between / and / in one or multiple lines.
Sees //, it ignores all text after // in the same line.
Sees /, it scans for the next / and ignores any text between / and /.
Specific meaning to the compiler.
Cannot be used for other purposes in the program.
Specify the properties of the data, methods, and classes.
Ex: public and static.
An action or a sequence of actions.
Ex: System.out.println("Welcome to Java!") is to display the greeting "Welcome to Java!" .
All statement ends with semicolon(;)
Forms a block that groups components of a program.
Performs a sequence of operations to display a message.
Template or blueprint for objects.
Essential Java construct.
The main() method must be declared to be public and static.
Style and convention
Block styles
Appropriate comments and comments style
Naming conventions
Proper indention and spacing
Single-Line Comments
End-Of-Line Comments
Block Comments
Two spaces should be used
Start with a character (A-Z, a-z), an underscore (_) or a dollar sign ($).
Keywords cannot be used as identifiers.
Special characters like #, !, @ and ^ cannot be used.
Simple and easy to understand.
runs on a wide variety of operating environments.