Ttykuu

I am trying to learn how to correctly structure my projects and write a good, clean code. I would also like to learn how to write good tests. Can you please review it and give me some tips and tricks how to make that better?

The application is calculating the exchange from the bill for lemonade. Lemonade costs 5$ and client may pay with 5$, 10$ or 20$. At the beginning there is no change available.

Project structure

My project structure is as follows:

LemonadeChange (project) with src package and 4 packages inside:

• app (contains Main)


• calculatorImp (contains CalculatorLongImp and CalculatorShortImp)


• calculatorInterface (contains CalculatorInterface)


• test (contains CalculatorTest)

Classes

Main

public class Main 

public static void main(int[] args) 
 CalculatorInterface calc = new CalculatorLongImp();
 calc.lemonadeChange(args);

CalculatorInterface

public interface CalculatorInterface 

public boolean lemonadeChange(int[] bills);

CalculatorLongImp

public class CalculatorLongImp implements CalculatorInterface 
private int five = 0;
private int ten = 0;
int acc = 0;

public boolean lemonadeChange(int[] bills) 
 for (int bill : bills) 
 if(bill == 5) 
 five++;
 
 else if(bill == 10) 
 five--;
 ten++;
 
 else 
 if(ten >= 1 && five >= 1) 
 ten--;
 five--;
 
 else if (five >= 3) 
 five -= 3;
 
 else 
 acc++;
 
 
 

 if(acc == 0) 
 return true;
 
 else 
 return false;
 

CalculatorTest

public class CalculatorTest 

@Test
public void testAllChangeShouldBePossibleToGive() 
 int[] bills = 5,5,5,10,20;
 CalculatorInterface calc = new CalculatorLongImp();
 assertTrue(calc.lemonadeChange(bills));
 calc = new CalculatorShortImp();
 assertTrue(calc.lemonadeChange(bills));


@Test
public void testAllChangeShouldNotBePossibleToGive() 
 int[] bills = 20;
 CalculatorInterface calc = new CalculatorLongImp();
 assertFalse(calc.lemonadeChange(bills));
 calc = new CalculatorShortImp();
 assertFalse(calc.lemonadeChange(bills));


@Test
public void testAllChangeShouldNotBePossibleToGiveSecond() 
 int[] bills = 10, 20;
 CalculatorInterface calc = new CalculatorLongImp();
 assertFalse(calc.lemonadeChange(bills));
 calc = new CalculatorShortImp();
 assertFalse(calc.lemonadeChange(bills));


@Test
public void testAllChangeShouldBePossibleToGiveSecond() 
 int[] bills = 5, 5, 10, 20;
 CalculatorInterface calc = new CalculatorLongImp();
 assertTrue(calc.lemonadeChange(bills));
 calc = new CalculatorShortImp();
 assertTrue(calc.lemonadeChange(bills));


@Test
public void testAllChangeShouldNotBePossibleToGiveThird() 
 int[] bills = 10, 20, 5, 5;
 CalculatorInterface calc = new CalculatorLongImp();
 assertFalse(calc.lemonadeChange(bills));
 calc = new CalculatorShortImp();
 assertFalse(calc.lemonadeChange(bills));


@Test
public void testAllChangeShouldBePossibleToGiveThird() 
 int[] bills = 5,5,5,5,20;
 CalculatorInterface calc = new CalculatorLongImp();
 assertTrue(calc.lemonadeChange(bills));
 calc = new CalculatorShortImp();
 assertTrue(calc.lemonadeChange(bills));

How would you improve that? Any tips and tricks welcomed!

Please let me know if you want to see the task that it solves - that is one of the tasks on LeetCode, so I can post it if that makes review easier.