Snippet Code

Question 1

Beware the closure:

What’s the output of this Javascript function?

function hookupevents() {
  for (var i = 0; i < 3; i++) {
    document.getElementById("button" + i)
      .addEventListener("click", function() {
        alert(i);
      });
  }
}

Question 2

Type Erasure:

About Type Erasure, what’s the output of this Java snippet, and why?

ArrayList li = new ArrayList();
ArrayList lf = new ArrayList();
if (li.getClass() == lf.getClass()) // evaluates to true
  System.out.println("Equal");

Question 3

Memory Leak

Can you spot the memory leak?

public class Stack {
    private Object[] elements;
    private int size = 0;
    private static final int DEFAULT_INITIAL_CAPACITY = 16;

    public Stack() {
        elements = new Object[DEFAULT_INITIAL_CAPACITY];
    }

public void push(Object e) {
    ensureCapacity();
    elements[size++] = e;
}

    public Object pop() {
        if (size == 0)
            throw new EmptyStackException();
        return elements[--size];
    }

    /**
     * Ensure space for at least one more element, roughly
     * doubling the capacity each time the array needs to grow.
     */
    private void ensureCapacity() {
        if (elements.length == size)
            elements = Arrays.copyOf(elements, 2 * size + 1);
    }
}

Question 4

Kill the switch:

ifs and in general conditional statements lead to procedural and imperative programming. Can you get rid of this switch and make this snippet more object-oriented?

public class Formatter {

private Service service;

    public Formatter(Service service) {
        this.service = service;
    }

    public String doTheJob(String theInput) {
        String response = service.askForPermission();
        switch (response) {
        case "FAIL":
            return "error";
        case "OK":
            return String.format("%s%s", theInput, theInput);
        default:
            return null;
        }
    }
}

Question 5

Kill the if:

Can you get rid of these ifs and make this snippet of code more object-oriented?

public class TheService {
private final FileHandler fileHandler;
private final FooRepository fooRepository;

    public TheService(FileHandler fileHandler, FooRepository fooRepository) {
        this.fileHandler = fileHandler;
        this.fooRepository = fooRepository;
    }

public String Execute(final String file) {

    final String rewrittenUrl = fileHandler.getXmlFileFromFileName(file);
    final String executionId = fileHandler.getExecutionIdFromFileName(file);

    if (executionId.equals("") || rewrittenUrl.equals("")) {
        return "";
    }

    Foo knownFoo = fooRepository.getFooByXmlFileName(rewrittenUrl);

    if (knownFoo == null) {
        return "";
    }

    return knownFoo.DoThat(file);
} }

Question 6

Kill the if-chain:

How would you refactor this code?

function()
{
    HRESULT error = S_OK;

    if(SUCCEEDED(Operation1()))
    {
        if(SUCCEEDED(Operation2()))
        {
            if(SUCCEEDED(Operation3()))
            {
                if(SUCCEEDED(Operation4()))
                {
                }
                else
                {
                    error = OPERATION4FAILED;
                }
            }
            else
            {
                error = OPERATION3FAILED;
            }
        }
        else
        {
            error = OPERATION2FAILED;
        }
    }
    else
    {
        error = OPERATION1FAILED;
    }

return error; }