Lesson 1.3 Expressions and Output

CSA Unit 1.3 — Expressions and Output

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Popcorn Hack 1

Task:
Recall as many key formatting tools as you can without referring to the notes above. List them and explain what each does.
Then, write a single line of code using as many of the tools as possible.

Answer:

\n → newline (moves text to the next line)
\t → tab (adds spacing)
\\ → prints a backslash
\" → prints a double quote
System.out.print() → prints text without moving to the next line
System.out.println() → prints text and moves to a new line
System.out.printf() → prints formatted text (e.g., decimals, alignment)

System.out.println("She said:\t\"Java\\CSA rocks!\"\nLet's code!");

She said:	"Java\CSA rocks!"
Let's code!

Popcorn Hack 2

Task:
What formatting tools are used in Menu.java?
How do they make the output cleaner/better?

Answer:

• System.out.println() → separates each menu option on a new line.
• System.out.print() → keeps the user input prompt (“Choose an option:”) on the same line.
• String concatenation (+) → combines variables with text dynamically.
• Escape sequences (====) → make the menu organized and visually clear.

Together, they create a clean, structured, and easy-to-read menu for users.

Homework Hack 1

System.out.print("AP ");
System.out.println("CSA");
System.out.println("Rocks!");

AP CSA
Rocks!

//Fixed bug code
System.out.println("C:\\Users\\Student");

C:\Users\Student

import java.util.Scanner;

public class Menu {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("=== Main Menu ===");
        System.out.println("1. Start Game");
        System.out.println("2. Instructions");
        System.out.println("3. Exit");
        System.out.println("4. Settings");
        System.out.print("Choose an option: ");
        int choice = sc.nextInt();
        System.out.println("You selected option: " + choice);

        int optionCount = 4;
        System.out.println("There are " + optionCount + " total options.");
    }
}

Challenge

System.out.printf("Pi = %.2f\n", Math.PI);

Pi = 3.14





java.io.PrintStream@2bf33799

Homework Hack 2

import java.util.Scanner;

public class CalculatorMenu {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.println("==== Calculator Menu ====");
        System.out.println("1. Add");
        System.out.println("2. Subtract");
        System.out.println("3. Multiply");
        System.out.println("4. Divide");

        System.out.print("Choose an option: ");
        int option = sc.nextInt();

        System.out.print("Enter first number: ");
        double num1 = sc.nextDouble();
        System.out.print("Enter second number: ");
        double num2 = sc.nextDouble();

        double result = 0;
        if (option == 1) result = num1 + num2;
        else if (option == 2) result = num1 - num2;
        else if (option == 3) result = num1 * num2;
        else if (option == 4) result = num1 / num2;

        System.out.println("Result: " + result);
    }
}

Homework Hack 2: Assignment vs Comparison Explanation

Task:
Write an explanation distinguishing between:

• Assignment operator (=)
• Comparison operator (==)
  Include code examples showing proper usage of each, and explain a common bug that occurs when these are confused.

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Answer:

1. Assignment Operator (=)

The assignment operator is used to store a value in a variable.
It evaluates the expression on the right side, then assigns that value to the variable on the left side.

Example: ```java int x = 5; // assigns the value 5 to x x = x + 2; // takes current value (5), adds 2, then stores 7 in x