Goodluck to anyone taking this upcoming java cert!
Feel free to use/fork my notesz

1. Good practice about user input

sc.nextLine(); // clear bufferr

After nextInt(), nextDouble(), next() → add sc.nextLine() to clear buffer

Even:

char answer = Character.toUpperCase(sc.next().charAt(0));

Scanner sc = new Scanner(System.in);
System.out.print("Enter age: ");
int age = sc.nextInt();           
sc.nextLine();
System.out.print("Enter name: ");
String name = sc.nextLine();      

2. Faster print

import static java.lang.System.out;

out.println("Hello, You!"); // this will work

3. Use "ESC" if CodeChum suggest keyword you don't want (Leads to faster type)

4. To make all files fit inside Main.java file, Make the other class package-private

So instead of:

public class Main {
    ...
}
public class Animal {
    ...
}

Make it:

public class Main {
    ...
}
class Animal {
    ...
}

5. FileWriter vs BufferedWriter?

FileWriter: Writes directly to file, character by character.
BufferedWriter: Uses internal buffer (8KB default), writes in chunks.

In practice: No difference in output.

FileWriter is simpler for single writes.
BufferedWriter is faster for many writes (e.g., loops, large data).

Both work with \n:

FileWriter → write("text\n")
BufferedWriter → write("text\n") or newLine()