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Intermediate Java

Lesson 1: Introduction

Goals of this class

  • Getting to know each other
  • Get familiar with schedule, attendance, tools
  • Course introduction
  • Check required software (Java & Intellij Idea)
  • Iteration control structures recap (loops)
  • Do some basic Java exercises 🤩

General info

  • 📓 Course certificate only after minimum 80% attendance
  • 💨 We don’t show up late to class (and inform otherwise)
  • 🏝 We take a 10 minutes break in the middle of the class
  • 🕺🏻 We are here for you! Always ask questions if something is not clear.
  • 🚀 Never forget the feedback!
  • 🕸 Web, Previous Semesters
  • 🐦 Slack: #22s_programming_java
  • 🎓 We will have a Project at the end of the course!

Content of this course

We planned to cover the following topics over the course of the semester. However, it is important to note that this is not set in stone. Depending on the progress of the class as a whole, we may cover a bit more or a bit less. It is nevertheless most important that we work and progress as a group whilst helping one another grow.

  • The Java language
  • Data structures
  • Object Oriented Programming
  • Exceptions
  • Libraries
  • Build Tools
  • Unit Testing
  • File IO

Which tools we will be using?

All tools we use are described in the Initial Setup page.

At this point, we expect you have all of them installed and running, but if you didn’t make it ask the teachers on Slack.

Important: The focus of this course is not teaching you the tools, so we will show you only the basics, along with the content.

Iteration Control Structures Recap

Let’s review what we learned in the Introduction to Java course.

FOR loops

For loops are the most commonly used iteration control structures in Java (and other languages).

Their structure is as follows:

for (<INITIALIZATION>; <CONDITION>; <INCREMENT>) {
    // <CODE TO EXECUTE>
}

For loops are usually used to run <CODE TO EXECUTE> a given amount of times. They are using an INITIALIZATION statement which is run exactly once at the beginning, a CONDITION statement which is run before each iteration and an INCREMENT statement which is run after each iteration. For loops are executed until CONDITION evaluates to false. If they are false from the beginning, the code will never be executed.

Example:

public class SimpleForLoopExample {

    public static void main(String[] args) {

        for (int i = 0; i < 10; i++) {
            System.out.println("i is " + i);
        }
    }
}

WHILE loops

While loops are usually used to run code until a condition is not met anymore.

Structure:

while (<CONDITION>) {
    <CODE TO EXECUTE>
}

While the CONDITION evaluates to true, the code will be executed. Usually the CODE TO EXECUTE has an impact on the CONDITION, e.g. modifies its outcome.

Example:

import java.util.Scanner;

public class NumberGuessingGame {

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

        int numberToGuess = 19;
        boolean numberGuessed = false;
        int neededTries = 0;

        while (!numberGuessed) {
            neededTries++;
            System.out.println("Please guess a number between 0 and 20");

            int guessedNumber = input.nextInt();

            if (guessedNumber == numberToGuess) {
                numberGuessed = true;
            }
        }

        System.out.println("Congratulations! You needed " + neededTries + " tries to guess the given number!");
    }
}

DO-WHILE loops

Do-while loops are the least used ones. Unlike while loops, they guarantee at least one code execution.

Structure:

do {
    <CODE TO EXECUTE>
} while(<CONDITION>);

The CODE TO EXECUTE will first be executed once, then the CONDITION will be evaluated. This is repeated until the CONDITION evaluates to false.

Example:

import java.util.Scanner;

public class NumberGuessingGame {

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

        int numberToGuess = 19;
        boolean numberGuessed = false;
        int neededTries = 0;
        
        do {
            neededTries++;
            System.out.println("Please guess a number between 0 and 20");

            int guessedNumber = input.nextInt();

            if (guessedNumber == numberToGuess) {
                numberGuessed = true;
            }          
        } while (!numberGuessed);

        System.out.println("Congratulations! You needed " + neededTries + " tries to guess the given number!");
    }
}

Exercises

Exercise 1: Multiples of 3 or 5

If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below 1000.

Original Source

Exercise 2: Smallest Multiple

2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder.

What is the smallest positive number that is evenly divisible by all the numbers from 1 to 20?

Original Source

Supporting Materials:

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