Java Basics Recap: Key Learnings Thus Far

Alright, today is all about recapping what I’ve learned from Day 1 to Day 4 of my Java journey. It’s time to reflect, refresh, and remind myself that I am slowly but surely becoming a Java pro (or at least less confused than before).

Day 1: Java Basics – Setting the Foundation

Ah, the day I officially stepped into the Java world. Here’s what I learned:

☕ JDK, JRE, and JVM – The Holy Trinity of Java

JDK (Java Development Kit): The full package – includes everything I need to write, compile, and run Java code.
JRE (Java Runtime Environment): Only helps in running Java programs, but can’t compile them.
JVM (Java Virtual Machine): The real MVP, it runs Java programs by converting them into bytecode that computers understand.

🧠 Memory Management in Java

Stack Memory: Stores method calls and local variables (used for fast execution).
Heap Memory: Stores objects and dynamic data.
Garbage Collector: Automatically deletes unused objects (so I don’t have to clean up my own mess).

🖥 Taking Input & Printing Output

Used Scanner to take input:

  import java.util.Scanner;

  public class InputExample {
      public static void main(String[] args) {
          Scanner sc = new Scanner(System.in);
          System.out.print("Enter your name: ");
          String name = sc.nextLine();
          System.out.println("Hello, " + name + "!");
      }
  }

Printed output using System.out.println() (which I’ve now typed a million times).

🔄 Conditionals & Loops

if-else statements to make decisions.
for loop, while loop, do-while loop to run code multiple times (aka repeat the pain).

Day 2: Functions and Methods – Reusing Code Like a Pro

This day was all about writing functions (also called methods) to avoid writing the same code over and over again.

What is a Function?

A function is a block of code that performs a specific task and can be reused. It reduces code repetition and makes life easier.

How to Define a Function in Java?

public static void greet() {
    System.out.println("Hello, welcome to Java!");
}

Here,

public: Anyone can access it.
static: Can be used without creating an object.
void: Doesn’t return anything.
greet(): Function name.

How to Call a Function?

public static void main(String[] args) {
    greet();  // Calling the function
}

And boom! It prints:

Hello, welcome to Java!

Functions with Parameters (Passing Values)

public static void sum(int a, int b) {
    System.out.println("Sum: " + (a + b));
}

Calling sum(5, 10); prints:

Sum: 15

Functions that Return Values

public static int multiply(int x, int y) {
    return x * y;
}

Calling multiply(3, 4); returns 12.

Day 3: Arrays – Storing Multiple Values Like a Boss

Now, let’s talk about arrays, because apparently, storing a single value in a variable wasn’t enough.

What is an Array?

An array is like a container that holds multiple values of the same type.

Declaring and Initializing an Array

int[] numbers = {10, 20, 30, 40, 50};

Here, numbers is an array that stores 5 integers.

Accessing Elements in an Array

Each element in an array has an index (starting from 0):

System.out.println(numbers[0]);  // Output: 10
System.out.println(numbers[3]);  // Output: 40

Looping Through an Array

for (int i = 0; i < numbers.length; i++) {
    System.out.println(numbers[i]);
}

This prints all elements of the array.

Modifying an Array

numbers[2] = 100;  // Changes the third element (index 2) to 100

Day 4: Switch Statements – The If-Else Alternative

If if-else statements were annoying, then meet switch statements, which make code cleaner and easier to read.

Basic Switch Statement

int day = 3;

switch (day) {
    case 1:
        System.out.println("Monday");
        break;
    case 2:
        System.out.println("Tuesday");
        break;
    case 3:
        System.out.println("Wednesday");
        break;
    default:
        System.out.println("Invalid Day");
}

Output:

Wednesday

The break statement prevents fall-through (i.e., stopping execution after the correct case runs).
The default case runs when no case matches.

Nested Switch (Switch Inside a Switch 🤯)

int branch = 2;
int year = 3;

switch (branch) {
    case 1:
        System.out.println("CSE");
        switch (year) {
            case 1:
                System.out.println("First Year");
                break;
            case 2:
                System.out.println("Second Year");
                break;
        }
        break;
    case 2:
        System.out.println("IT");
        break;
}

If branch = 1 and year = 2, the output will be:

CSE
Second Year

Final Thoughts

So, in just 4 days, I’ve learned:
✅ How Java works (JDK, JRE, JVM)
✅ How to take input and print output
✅ How to use if-else and loops
✅ How to write functions and reuse code
✅ How to store multiple values using arrays
✅ How to write cleaner code using switch statements

Today’s recap day really helped me reinforce my knowledge, and I’m excited for what’s next! 🚀

That’s all for today! Tomorrow, I’ll be back with more Java adventures. 😎

Day 5: Recap of Java Basics – Everything I’ve Learned So Far!

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