Java Basics Lecture Notes

Introduction

• Purpose: Teach Java basics
• Encouragement to like, comment, subscribe
• Topics include Java essentials, installation, IDE usage, tips, and tricks.

Importance of Learning Java

• Top 3 most popular programming languages
• Flexible: used in enterprises, Android apps, games.
• Career prospects: Java developers have high starting salaries ($70,000+ according to Glassdoor).

Basics of Computer Languages

• High-level vs Low-level Languages: Computers understand binary (machine code), difficult for humans.
• Source Code: Human-readable, compiled to machine code.
• Java Source Code: Ends with .java, compiled to bytecode (.class) which is platform-independent.

Compiling Java

• Bytecode: Intermediate, cross-platform format, executed by JVM (Java Virtual Machine).
• JVM: Part of JDK (Java Development Kit) which includes JRE (Java Runtime Environment) and development tools.

Setting Up Java

• Downloading JDK: Search "Java JDK download", choose the correct version for your OS.
• IDE Recommendations: Eclipse or IntelliJ IDEA.
  • Instructions for downloading and setting up Eclipse.

Creating a Java Project

• Start a Project: Create Java project in IDE, name it uniquely.
• Configure JRE: Ensure it's set to the version you downloaded.

Writing Java Code

• Classes and Methods: Create a class, typically named 'Main'. Include public static void main(String[] args).
• Printing to Console: Use System.out.print and System.out.println for output.
  • Escape sequences like \n (newline), \t (tab).

Comments in Java

• Single-line Comment: Begin with //
• Multi-line Comment: Enclosed between /* and */

Tips and Tricks

• Changing IDE themes for better visibility
• Shortcuts for print statements and replacing text in code.

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Java Variables and Data Types

Variables

• Variables: placeholders for values, behave as contained value.
• Types: numeric, boolean, string, etc.

Data Types

• Primitive Types: boolean, byte, short, int, long, float, double, char.
  • Integers, floating points, boolean (true/false), and characters.
• String: Reference data type, sequence of characters.

Declaring Variables

• Declaration: Specify data type and name.
• Assignment: Assign a value to the variable.
• Initialization: Combine declaration and assignment.

Working with Variables

• Print variables, concatenate with strings.
• Integer limits, using long for large numbers.
• Using float or double for decimal numbers.

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Java Input and Output

User Input

• Scanner Class: Accepts input, need to import java.util.Scanner.
• Create scanner object, prompt for input, and read strings, integers, etc.
• Handle input mismatch exceptions.

Graphical User Interface (GUI)

• JOptionPane: Create input and message dialog boxes.
• Collect input through dialogs and display messages.

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Java Expressions and Math

Expressions

• Components: Operands (values) and operators (arithmetic symbols).
• Arithmetic Operations: Addition, subtraction, multiplication, division, modulus.

Math Class Methods

• Methods for mathematical operations (max, min, abs, sqrt, ceil, floor).
• Project: Calculate the hypotenuse using Math.sqrt().

Random Numbers

• Random Class: Generate integers, doubles, booleans.
• Use import java.util.Random and create random instances.

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Conclusion

• Practice creating Java projects and using variables, input/output, expressions.
• Explore GUI and more advanced Java features with continued learning.