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Activity 1.2 Arithmetic

Introduction

Activity 1.2

Arithmetic

Topics

Arithmetic in programming
Numeric Types: integer and double
Math operators
Operator precedence

Arithmetic in programming

Any useful program, from video games to online stores, relies on numbers.

Whether it's calculating scores, processing transactions, or generating graphics, math is everywhere in software.

Numeric Types: Integer and Double

In Java, numbers are categorized as either integers (for whole numbers) or doubles (for decimal numbers).

2.5 401 -65 -123.45 1_000_000 "35"

Demo

Use the System.out.println() method to display some numbers on the screen.

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public class DemoProgram {
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    public static void main(String[] args) {
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        System.out.println(303);
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        System.out.println(-25.2);
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        System.out.println(1_000_000);
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    }
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}

Math Operators

+ Addition

- Subtraction

* Multiplication

/ Division: Divides two numbers and returns an integer when both numbers are integers, and a double when at least one of the numbers is a double.

% Modulus (Mod): Divides two numbers and returns the remainder.

Division Operations with Integers and Doubles

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public class DemoProgram {
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    public static void main(String[] args) {
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        System.out.println(100 / 2);
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        System.out.println(14 / 3);
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        System.out.println(20 / 6.0);
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        System.out.println(10.0 / 2.5);
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        System.out.println(10 % 4);
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    }
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}

Demo: Divide Integers and Doubles

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public class DemoProgram {
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    public static void main(String[] args) {
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        System.out.println(100 / 2);
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        System.out.println(14 / 3);
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        System.out.println(20 / 6.0);
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        System.out.println(10.0 / 2.5);
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        System.out.println(10 % 4);
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    }
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}

1
50
2
4
3
3.3333333333333335
4
4.0
5
2

Operator Precedence

Java follows typical order of operations rules, include parenthesis.

3 * 4 + 5

3 * (4 + 5)

Key Terms

Data Type: A classification for different kinds of information. It tells you what kind of data is being stored or used.
Integer: A data type that stores whole numbers, like 5, 25, or -100.
Double: A data type that stores numbers with decimal points, like 3.14 or -99.99.

'F' → Fullscreen

Objectives

Evaluating math expressions
Displaying numeric output

Activity Tasks

Create a new Java project named 1-2-Arithmetic.
Complete each task individually.

Task 1: Addition, Subtraction, and Multiplication

Display the result of the math expressions using System.out.println().

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public class Program {
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    public static void main(String[] args) {
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        // Addition
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        System.out.println("I'm adding 2 and 1. The result is:");
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        System.out.println(2 + 1);
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        System.out.println();
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        System.out.println("Adding $1000 and $500.96 gives us:");
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        System.out.println(1000 + 500.96);
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        System.out.println();
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        // Subtraction
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        System.out.println("I have 3 apples, and I eat one. Now, I have:");
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        System.out.println(3 - 1);
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        System.out.println();
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        // Multiplication
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        System.out.println("I'm 30 years old. In months, that's: ");
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        System.out.println(30 * 12);
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        System.out.println();
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//
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    }
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}

Task 2: Division

Practice the various division operations. Take note of the result when using integers and/or doubles.

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public class Program {
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    public static void main(String[] args) {
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        // Addition
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        System.out.println("I'm adding 2 and 1. The result is:");
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        System.out.println(2 + 1);
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        System.out.println();
7

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        System.out.println("Adding $1000 and $500.96 gives us:");
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        System.out.println(1000 + 500.96);
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        System.out.println();
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        // Subtraction
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        System.out.println("I have 3 apples, and I eat one. Now, I have:");
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        System.out.println(3 - 1);
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        System.out.println();
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        // Multiplication
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        System.out.println("I'm 30 years old. In months, that's: ");
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        System.out.println(30 * 12);
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        System.out.println();
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        // Division with integers and doubles
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        System.out.println("If we divide 8 pizza slices between 2 people, each person gets:");
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        System.out.println(8 / 2);
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        System.out.println();
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        System.out.println("Dividing $100 among 6 people gives each person:");
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        System.out.println(100.0 / 6);
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        System.out.println("Without fractional amounts, each person gets:");
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        System.out.println(100 / 6);
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        System.out.println();
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        // Remainder using the mod operator
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        System.out.println("After dividing $100 among 6 people, the leftover cents are:");
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        System.out.println(100 % 6);
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        System.out.println();
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//
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    }
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}

Task 3: Operator precedence

Practice using parenthesis to control the order of operations.

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public class Program {
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    public static void main(String[] args) {
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        // Addition
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        System.out.println("I'm adding 2 and 1. The result is:");
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        System.out.println(2 + 1);
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        System.out.println();
7

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        System.out.println("Adding $1000 and $500.96 gives us:");
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        System.out.println(1000 + 500.96);
10
        System.out.println();
11

12
        // Subtraction
13
        System.out.println("I have 3 apples, and I eat one. Now, I have:");
14
        System.out.println(3 - 1);
15
        System.out.println();
16

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        // Multiplication
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        System.out.println("I'm 30 years old. In months, that's: ");
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        System.out.println(30 * 12);
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        System.out.println();
21

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        // Division - Quotient and remainder
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        // Quotient
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        System.out.println("If we divide 8 pizza slices between 2 people, each person gets:");
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        System.out.println(8 / 2);
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        System.out.println();
27

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        System.out.println("Dividing $100 among 6 people gives each person:");
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        System.out.println(100.0 / 6);
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        System.out.println("Without fractional amounts, each person gets:");
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        System.out.println(100 / 6);
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        System.out.println();
33

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        // Remainder using the modulus, or mod, operator
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        System.out.println("After dividing $100 among 6 people, the leftover cents are:");
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        System.out.println(100 % 6);
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        System.out.println();
38

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        // Order of operations
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        System.out.println("The expression 4 * 10 + 12 equals:");
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        System.out.println(4 * 10 + 12);
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        System.out.println("The expression 4 * (10 + 12) equals:");
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        System.out.println(4 * (10 + 12));
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//
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    }
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}

Sample Output

Your program output should something similar to the sample output below.

I'm adding 2 and 1. The result is:
3

Adding $1000 and $500.96 gives us:
1500.96

I have 3 apples, and I eat one. Now, I have:
2

I'm 30 years old. In months, that's:
360

If we divide 8 pizza slices between 2 people, each person gets:
4

Dividing $100 among 6 people gives each person:
16.666666666666668
Without fractional amounts, each person gets:
16

After dividing $100 among 6 people, the leftover cents are:
4

The expression 4 * 10 + 12 equals:
52
The expression 4 * (10 + 12) equals:
88

Reflection Questions

You may write your reflection answers as comments at the bottom of your code.

What's the difference between the / operator and the % operator, and when would you use each one? Use an example from the lesson to support your answer.
Explain why it's important to differentiate between whole numbers (integers) and decimal numbers (doubles) when writing code. How did using a decimal number change the output of a division problem in this activity?
The lesson shows that 4 * 10 + 12 and 4 * (10 + 12) produce different results. Why is it important to use parentheses in an expression, and what do they do?

Submission

Submit your activity and reflection answers to the appropriate dropbox.