# 01 - Introduction to Intermediate Java Course

Maciej Walkowiak

# Goals

• Get familiar with schedule, attendance, teachers, tools
• Get to know each other
• Course introduction
• Install required software
• Learn how to create a new project with IntelliJ
• Do some basic Java exercises!

# Slides

# Java Basics Recap

package com.redi.j2;

public class Main {

    public static void main(String[] args) {
        System.out.println("Hello World");

        String name = "Memet";
        String profession = "skydiver";
        int age = 40;
        boolean smoking = false;

        someMethod(profession);

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

    private static void someMethod(String profession) {
        if (profession.equals("skydiver")) {
            System.out.println("Cool");
        } else {
            System.out.println("not cool");
        }
    }
}

# Exercises

Same exercises as on slides, copied here for convenience.

# Exercise 1

Write a method that for X and Y given by arguments prints square of each number between X and Y.

2 - 4
3 - 9
… 

Solution:

private static void squares(int x, int y) {
    for (int i = x; i < y; i++) {
        System.out.println(i + " - " + (i * i));
    }
}

# Exercise 2

In Polish language there is a rule that if name ends with “a” it’s a female name, if not it’s a male name.

Write a method that checks if Polish name given by variable is a male or female

For example:

Krysian - male

Solution:

private static void polishNames(String name) {
    if (name.endsWith("a")) {
        System.out.println(name + " is a girl");
    } else {
        System.out.println(name + " is a boy");
    }
}

# Exercise 3

Write a method that for X and Y, for each number between X and Y writes a number and if its odd or even.

Solution:

private static void evenOrOdd(int x, int y) {
    for (int i = x; i < y; i++) {
        String isEvenOrOdd = i % 2 == 0 ? "even" : "odd";
        System.out.println(i + " is " + isEvenOrOdd);
    }
}

# Exercise 4

Write a method that for age given by parameter prints if is underage (and then how many years left until becomes an adult), or adult, if can buy a beer.

In Germany you become an adult at 18 but you can buy a beer already when you’re 16.

Solution:

private static void beer(int age) {
    int yearsUntilAdult = 18 - age;
    if (age > 18) {
        System.out.println("An adult, can buy a beer");
    } else if (age > 16) {
        System.out.println("Not an adult, but can buy a beer.");
    } else {
        System.out.println("Underage, cannot buy a beer");
    }
    if (yearsUntilAdult > 0) {
        System.out.println("He will be an adult in  " + yearsUntilAdult + " years.");
    }
}

# Exercise 5

Write a method that calculates how much money stays in the pocket of a freelancer in Poland. Each freelancer has to pay 300 EUR insurance and income tax is flat 19%.

For example, if freelancer made 5000 EUR, in his pocket stays 4700 * 81% = 3807 EUR.

Solution:

private static void inPocket(int income) {
    int profit = income - 300;
    System.out.println("In pocket stays " + (int) (profit * 0.81));
}

# Homework

Write a program that for given value of variable “height” will print out right-half of the christmas tree to the console.

• Tree starts with “I” on the top and ends with “M” on the bottom.
• Tree is built from “X” and “Y” characters one after another

For example for height equals 6 it will print:

I
XY
XYX
XYXY
XYXYX
M

package com.example.demo;

public class TreeExercise {

    public static void main(String[] args) {
        int height = 8;

        // put your code here
    }
}

private static void tree(int height) {
    System.out.println("I");
    for (int i = 2; i < height; i++) {
        for (int j = 0; j < i; j++) {
            System.out.print(j % 2 == 0 ? "X" : "Y");
        }
        System.out.println();
    }
    System.out.println("M");
}

Thx to Elena - even better - way way more optimised solution:

public static void tree(int a) {
    System.out.println("I");
    String step = "X";

    for (int i = 2; i < a; i++) {
        step = i%2 == 0 ? step + "Y" : step + "X";
        System.out.println(step);
    }
    System.out.println("M");
}

# Additional Resources

• Is the use of Java's default package a bad practice?
• Base CS - Exploring the basics of computer science, every Monday, for a year.
• Base CS Podcast
• Object Oriented Programming with Java Part 1 - Free Online Course
• W3Schools Java Tutorial