Java Basics Quiz

Fundamentals of Programming

• This is a course on programming fundamentals.
• The instructor is Dr. Ako Muhammad Abdullah.
• The course is offered at the University of Sulaimani.

Chapter One: Variables

• Variables are data containers holding data during program execution.
• Each variable has a data type defining its value type.
• A variable is a memory location name.
• Variable values can change during program execution.

What is Java?

• Java is a high-level, object-oriented programming language.
• It's widely used for building applications.
• Applications include web, mobile, and enterprise systems.
• Java programs run on any device with a Java Virtual Machine (JVM).
• Oracle owns Java.

Applications of Java

• Web applications use technologies such as Spring, Hibernate, and JSP/Servlets.
• Java is widely used in enterprise solutions like banking and insurance.
• Android apps primarily use Java.
• Java runs on small devices like smart cards.
• Many 2D/3D games also use Java frameworks like LibGDX.
• Java is used for scientific applications in simulations, modeling, and data analysis.

Key Features of Java

• Platform independence: Java code compiles into bytecode that runs on any system with a JVM.
• Object-oriented: Java is based on objects representing real-world entities, having attributes (states) and behaviors (methods).
• Robust and secure: Java has strong memory management, exception handling, and built-in security.
• Simple and easy to learn: Java's syntax is similar to C/C++ but avoids complex features like pointers and manual memory management.
• Multithreaded: Java supports concurrent programming, allowing multiple threads to execute simultaneously.
• Open-source and free.
• Distributed and Network-Centric: Java supports APIs for networking and distributed systems, which is great for web and enterprise applications.

Popular Java Editors

• Notepad++, TextPad (Windows simple text editors).
• NetBeans (open-source, free Java IDE).
• Eclipse (open-source, community-developed Java IDE).

Java - Basic Syntax

• Java programs consist of objects that communicate through methods.
• An object is an instance of a class, possessing state (data) and behavior (actions).
• Creating an object (an instance of a class) involves calling the class's constructor.

Java - Basic Syntax (Cont'd)

• A class acts as a template for objects.
• Classes are created using the class keyword.
• A class name should match the file name containing the main method.
• The main method is the program's starting point.

Java - Basic Syntax (Cont'd 2)

• Java statements end with a semicolon (;).
• Comments are used for documentation (single-line: //, multi-line: /* */).
• Java is case-sensitive.
• Class names start with a capital letter, and method names start with a lowercase letter.

Working of Java Bytecode

• Java code compiles into bytecode, an intermediate language.
• Java Virtual Machine (JVM) interprets bytecode.
• JVM executes bytecode without CPU dependency.
• Java bytecode is machine-independent.
• Java Runtime Environment (JRE) is needed for bytecode execution.

Variables

• Variables are data containers holding values during program execution in Java.
• They have a data type, which determines what kind of data it can hold.
• Declaring a variable involves specifying its type and name.
• Variables are used to store data in a program.

Variable Declaration

• Declaring variables requires specifying a data type and name.
• Values are assigned using the = operator.

Variable Declaration (Cont'd)

• Datatype: Type of data variable stores.
• Variable Name: Name given to memory location.

General Rules for Naming Variables

• Variables can contain letters, digits, underscores, and dollar signs.
• Variable names start with letters or $ , _.
• Names should be lowercase with no spaces.
• Names are case sensitive (e.g myVar and myvar are different).
• Reserved words cannot be used as variable names

Types of Variables

• Local Variables: These are defined inside a block, method, or constructor.
• Instance Variables: These are defined inside a class outside methods.
• Static Variables: These are defined inside a class, but with the static keyword. They are associated with the class itself.

Static Variables

• Static variables are also Class variables.
• They are declared using the static keyword in a class outside any method or block.
• Only one copy of a static variable exists per class, regardless of the number of objects created.
• Initialized at the start of program; destroyed at the end.

Variable Initialization

• Variable initialization assigns values to variables.
• Explicit initialization assigns a value to a variable at the time of declaration.
• Default initialization assigns default values to variables automatically.
• Static Initialization Blocks can be used to initialize static variables with more complex logic.
• Dynamic Initialization assigns values at runtime.

Variable Initialization (Cont'd)

• Constructor Initialization: Instance variables are initialized during object creation through constructors.
• Important: Variables must be initialized before use or compilation will fail.

Some Examples of Variables

• Various Java variable declaration examples demonstrate usage with examples of different variable types and assigning values.

Display Variables

• Using the println() method to display variable values, including their combination with text using +.
• Example of displaying numeric and string variables.

Declare Many Variables

• Declaring multiple variables of the same type in a single line using a comma separator

Java Identifiers

• Java identifiers are unique names for variables.
• Use descriptive names for improved readability.