Java Full Course for Beginners

Java Full Course for Beginners - Note

1. Summary

This video is a comprehensive beginner-friendly Java course by Programming with Mosh. It covers installing Java, the basics of Java programming (variables, types, control flow), and concludes with a project: a mortgage calculator. The course aims to provide a solid foundation in Java for aspiring software developers. The instructor, Mosh, emphasizes clean coding practices and offers additional resources like a cheat sheet and a complete Java series for those wanting to deepen their knowledge.

2. Key Takeaways

* **Why Java?** Java is a popular, in-demand language for app and website development, and is well-suited for object-oriented programming (OOP).

* **Installation**: The video guides through the installation of the Java Development Kit (JDK) and a code editor (IntelliJ IDEA).

* **Anatomy of a Java Program**: Key elements include classes, methods (functions within a class), access modifiers (e.g., `public`), and the `main` method (entry point).

* **Data Types**: Covers primitive types (e.g., `byte`, `int`, `float`, `boolean`) and reference types (e.g., `String`, `Date`).

* **Control Flow**: Explains comparison, logical operators, conditional statements (`if`, `else`, `switch`), and loop constructs (`for`, `while`, `do-while`, "for-each").

* **Project: Mortgage Calculator**: A practical project is introduced to apply the learned concepts.

3. Detailed Notes

**0:00:00 - 0:03:59 Introduction and Setup**

* Course overview and goals: learn Java fundamentals.

* Installation of JDK (Java Development Kit).

* Download from Oracle.com

* Accept License Agreement

* Install

* Installation of IntelliJ IDEA (code editor).

* Download Community Edition (free).

* Drag and drop to Applications folder

**0:03:59 - 0:08:41 Anatomy of a Java Program**

* **Functions (Methods)**

* A block of code that performs a task.

* Structure: `returnType functionName(parameters) { // code }`

* `void` keyword for methods that do not return a value

* **Classes**

* Containers for related methods.

* Structure: `public class ClassName { // methods }`

* **Main Method**

* The entry point of a Java program.

* Should always be `public static void main(String[] args) {}` (Explanation of `static` will come later)

* **Access Modifiers**

* `public` is most common, determining accessibility from other classes/methods.

* Pascal naming convention for classes (e.g., `MainClass`).

* Camel naming convention for methods (e.g., `myMethod`).

**0:08:41 - 0:15:59 Your First Java Program**

* Creating a new Java project in IntelliJ.

* Project setup.

* Select Java and create a new project (Command Line application)

* Give the project a name

* Base package naming convention (`com.yourname`).

* Code breakdown

* `package` statement (specifies the package the class belongs to - must end with a semicolon (;)).

* `import` (for use of classes from other packages) - not needed if the classes are from the `java.lang` package.

* `System.out.println("Hello, World!");` - printing to console (The components of the System.out.println() method were explained).

* `Ctrl + R` (Mac Shortcut) to run the code.

**0:15:59 - 0:22:54 How Java Code Gets Executed**

* **Compilation:** IntelliJ uses the Java compiler (`javac`) to convert Java code (.java) to Java bytecode (.class).

* `javac main.java` creates `main.class` (bytecode).

* Bytecode is platform-independent

* **Execution:** The Java Virtual Machine (JVM) translates bytecode to native code for the operating system.

* JVM also known as Java Runtime Environment (JRE).

* `java com.codewithmosh.Main` executes the program. (Path to .class file is important here).

* **Five Interesting Facts about Java:**

* Developed by James Gosling (Sun Microsystems, 1995, later Oracle).

* Originally called "Oak", then "Green", then "Java".

* Different editions of Java (SE, EE, ME, Card).

* Has nearly 9 million developers worldwide.

* Average Java developer salary in US is over $100,000.

* Course Structure overview.

**0:22:54 - 0:25:22 Course Structure**

* Introduction to the course structure (4 parts).

* Part 1: Fundamentals

* Part 2: OOP

* Part 3: Java APIs

* Part 4: Advanced Java Features

**0:25:22 - 0:26:21 Types**

* Fundamentals covered in the first part.

**0:26:21 - 0:29:14 Variables**

* Variables used to temporarily store data.

* Syntax: `dataType variableName = initialValue;`

* `int age = 30;` (Example)

* Initializing variables.

* Multiple variables can be declared on the same line using commas, but this is not the best practice

* Copying values between variables

* CamelCase naming convention for variables (e.g., `myAge`)

**0:29:14 - 0:34:27 Primitive Types**

* Two categories of types:

* Primitive (simple values).

* Reference (complex objects).

* **Primitive Types:**

* `byte`: 1 byte (-128 to 127).

* `short`: 2 bytes.

* `int`: 4 bytes.

* Underscores used to make numbers readable (e.g., 1_000_000)

* L suffix for Long

* `long`: 8 bytes.

* `float`: 4 bytes. - F suffix

* `double`: 8 bytes.

* `char`: 2 bytes (single character, single quotes).

* `boolean`: `true` or `false`.

**0:34:27 - 0:39:15 Reference Types**

* Used to store complex objects.

* Examples:

* `Date now = new Date();` - need the "new" keyword for creating a new object of the Date class.

* Import statement (e.g., `import java.util.Date;`) - added automatically by IntelliJ.

* Using the dot operator to access members/methods of an object.

* `System.out.println(now);` to display the value of the object

**0:39:15 - 0:43:39 Primitive Types vs Reference Types**

* Key difference is memory management.

* Primitive types are copied by *value*.

* Reference types are copied by *reference* (the address in memory).

* Example:

* With primitives, changing one variable doesn't affect the other.

* With reference types, multiple variables can point to the same object. Changes via one variable are reflected in the others.

* `Point p1 = new Point(1, 1);` (Example, the members (x, y) of a class can be accessed using the dot operator)

* Reference types store the *reference* to the object in memory, not the object itself.

**0:43:39 - 0:50:42 Strings**

* `String` is a class (reference type).

* String literals.

* Examples: `String message = "Hello, World!";`

* Shorthand for creating strings (doesn't use `new`).

* String Concatenation: Using the `+` operator (e.g., `String message2 = message + "!!";`)

* Methods of the String class.

* `endsWith()`: Checks if a string ends with a specific sequence.

* `startsWith()`: Checks if a string starts with a specific sequence.

* `length()`: Returns the length (number of characters) of a string.

* `indexOf()`: Returns the index of the first occurrence of a character or substring (returns -1 if not found).

* `replace()`: Replaces characters or substrings (returns a new string, does not modify the original; strings are immutable in Java).

* `toLowerCase()`: Converts the string to lowercase (returns a new string).

* `toUpperCase()`: Converts the string to uppercase (returns a new string).

* `trim()`: Removes leading/trailing whitespace.

* **Escape Sequences:** Special characters within strings.

* `\"`: Double quote.

* `\\`: Backslash.

* `\n`: New line.

* `\t`: Tab.

**0:50:42 - 0:53:22 Arrays**

* Used to store a list of items of the same type.

* Syntax: `dataType[] arrayName = new dataType[size];` (Older Syntax)

* `int[] numbers = new int[5];` - creates an integer array of size 5

* To access a specific item, use an index (starting from 0).

* `numbers[0] = 1;`

* Exception when using an invalid index

* `Arrays.toString(numbers)` - for printing array elements.

* Arrays class.

* `import java.util.Arrays;`

* Newer Syntax

* `int[] numbers = {2, 3, 5, 1, 4};`

* `numbers.length;` returns the array's length (number of items in array)

* Arrays have a fixed length.

**0:53:22 - 0:58:47 Multi-Dimensional Arrays**

* Used to store matrices or cubes.

* Two-dimensional arrays.

* `int[][] matrix = new int[2][3];` - two rows and three columns (2X3 matrix)

* `Arrays.deepToString(matrix);` - for printing multi-dimensional arrays.

* Use two indexes to access an element (row, column).

* Three-dimensional arrays are also supported.

* Curly Brace Syntax

* `int[][] numbers = {{1, 2, 3}, {4, 5, 6}};` - A Matrix example.

**0:58:47 - 0:62:00 Constants**

* Final variables that cannot be changed.

* Declared with the `final` keyword.

* Naming convention: Use all uppercase letters (e.g., `final float PI = 3.14f;`).

**1:01:23 - 1:03:15 Arithmetic Expressions**

* Arithmetic Operators:

* `+` (addition), `-` (subtraction), `*` (multiplication), `/` (division), `%` (modulus - remainder).

* Operands

* Increment Operator (++) and Decrement Operator (--).

* Prefix and postfix application

* Compound assignment operators: `+=`, `-=`, `*=`, `/=`.

* Parentheses have the highest priority in the order of operations

**1:03:15 - 1:07:18 Order of Operations**

* Order of operations (PEMDAS/BODMAS):

* Parentheses

* Exponents

* Multiplication and Division (same precedence, evaluated left-to-right).

* Addition and Subtraction (same precedence, evaluated left-to-right).

**1:07:18 - 1:08:40 Casting**

* Type Conversion

* Implicit (Automatic Conversion)

* Conversion to a "wider" type (e.g., `short` to `int`) is automatic. No chance for data loss

* Explicit (Manual Conversion)

* When converting to a "narrower" type or between incompatible types. Can lead to data loss.

* Syntax: `(targetDataType) expression;` (e.g., `int y = (int) 3.1;`).

**1:08:40 - 1:15:08 The Math Class**

* Defined in `java.lang` (automatically imported).

* Methods:

* `round()`: Rounds a `float` to an `int` or a `double` to a `long`.

* `ceil()`: Returns the smallest `double` value that is greater than or equal to the argument.

* `floor()`: Returns the largest `double` value that is less than or equal to the argument.

* `max()`: Returns the greater of two values (various overloads for different numeric types).

* `min()`: Returns the smaller of two values (various overloads).

* `random()`: Returns a random `double` value between 0.0 (inclusive) and 1.0 (exclusive).

* Used with multiplication to get a random number within a specific range, (e.g., `int x = (int) (Math.random() * 100)` for a random number between 0-99.

* Use parentheses to make code readable

**1:15:08 - 1:19:50 Formatting Numbers**

* The `NumberFormat` class (in `java.text`).

* `NumberFormat currency = NumberFormat.getCurrencyInstance();` (Example)

* Cannot use the new operator to instantiate (abstract class).

* Use factory methods like `getCurrencyInstance()`, `getPercentInstance()`.

* `format()` method (e.g., `String result = currency.format(1234567.891);`)

* `NumberFormat percent = NumberFormat.getPercentInstance();`

**1:19:50 - 1:25:40 Reading Input**

* The `Scanner` class (in `java.util`).

* `Scanner scanner = new Scanner(System.in);` - creates a Scanner object.

* Methods for reading input from the terminal.

* `nextByte()`

* `nextShort()`

* `nextInt()`

* `nextFloat()`

* `nextDouble()`

* `next()`: Reads the next token (word).

* `nextLine()`: Reads the entire line (including spaces).

* `trim()` - used to remove white spaces before and after a string variable.

**1:25:40 - 1:32:55 Project: Mortgage Calculator**

* A project example to demonstrate all the concepts learned so far.

* Formula for Mortgage Calculation (Principal x (MonthlyInterestRate x (1 + MonthlyInterestRate)^NumberOfPayments) / ((1 + MonthlyInterestRate)^NumberOfPayments - 1)

**1:32:55 - 1:37:14 Solution: Mortgage Calculator**

* Review of the Mortgage Calculator example code implementation.

**1:37:14 - 1:38:43 Types Summary**

* Summary of types covered.

**1:38:43 - 1:46:00 Control Flow**

* Overview of control flow concepts.

**1:39:30 - 1:39:38 Comparison Operators**

* For comparing primitive values.

* `==` (Equality).

* `!=` (Inequality).

* `>` (Greater than).

* `<` (Less than).

* `>=` (Greater than or equal to).

* `<=` (Less than or equal to).

* Boolean expression produces a boolean value.

**1:39:38 - 1:41:16 Logical Operators**

* Used to combine boolean expressions (results in a boolean).

* `&&` (Logical AND).

* `||` (Logical OR).

* `!` (Logical NOT).

**1:41:16 - 1:50:18 If Statements**

* Allow programs to make decisions.

* `if (condition) { // code block }`

* `else if (condition) { // code block }`

* `else { // code block }`

* Structure of an if statement: `if`, `else if`, `else` clauses

* Best practice: Place `else if` and `else` on the same level

**1:50:18 - 1:53:47 Simplifying If Statements**

* Simplification of if statements: Removing unnecessary code.

* Boolean Expression

**1:53:47 - 1:56:16 The Ternary Operator**

* Compact way to express conditional logic when assigning values.

* `condition ? valueIfTrue : valueIfFalse;`

**1:56:16 - 2:00:07 Switch Statements**

* Used to execute different code based on the value of an expression.

* `switch (expression) { case value1: // code; break; case value2: // code; break; default: // code; }`

* Must include break statement to prevent the next case statement from being executed

* Switch statements can use byte, short, int and String types

**2:00:07 - 2:06:05 Exercise: FizzBuzz**

* Exercise: Write a program that:

* Reads an integer input.

* Prints "Fizz" if divisible by 5.

* Prints "Buzz" if divisible by 3.

* Prints "FizzBuzz" if divisible by both 5 and 3.

* Prints the number itself otherwise.

**2:06:05 - 2:09:53 For Loops**

* Used to execute code repeatedly.

* `for (initialization; condition; increment) { // code block }`

* Initialization (executed once at the beginning).

* Condition (boolean expression, loop continues if true).

* Increment (executed at the end of each iteration).

* loopCounter to count how many times a loop is executed

**2:09:53 - 2:14:19 While Loops**

* Similar to for loops, different syntax.

* `while (condition) { // code block }`

* Used when the number of iterations is not known in advance.

**2:14:19 - 2:15:36 Do...While Loops**

* Guaranteed to execute at least once.

* `do { // code block } while (condition);`

**2:15:36 - 2:18:52 Break and Continue**

* `break`: Terminates the loop.

* `continue`: Skips the current iteration and goes to the next iteration

**2:18:52 - 2:21:59 For-Each Loop**

* Used to iterate over arrays or collections.

* `for (dataType item : arrayName) { // code block }`

* Limited features: only forward, no index access.

**2:21:59 - 2:23:27 Project: Mortgage Calculator**

* Continuing the Mortgage Calculator Project and implementing Error handling to the code

**2:23:27 - 2:28:28 Solution: Mortgage Calculator**

* Solution walkthrough and code explanation.

* Implementation of error handling (using `while(true)` loops and `if` statements to check input validity).

**2:28:28 - 2:29:25 Control Flow Summary**

* Recap of Control flow concepts.

**2:29:25 - 2:30:49 Clean Coding**

* Introduction to clean coding principles: