renanreismartins

public void criaInterface() {
  
  String var = "content";
  
  botao.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View view) {
      System.out.println(var); // ERRO!
    }
  });

renanreismartins

public void criaInterface() {
  
  final String var = "content";
  
  botao.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View view) {
      System.out.println(var); // OK!
    }
  });

renanreismartins

 @Before
  public void setup() {
    names = new ArrayList<Option<String>>();
    names.add(new Some<String>("Renan"));
    names.add(new None<String>());
    names.add(new Some<String>("Paulo"));
  }
  
    @Test
  public void usandoGetOrElse() {

renanreismartins

  @Test
  public void verificaSePossuiValor() {
    String[] expected = { "Renan", null, "Paulo"};

    for (int i = 0; i < names.size(); i++) { 
      Option<String> option = names.get(i);
      
      if (option.hasValue()) {
        String value = option.get();
        System.out.println(option + " = " + value);

renanreismartins

public Option<String> fazAlgo() {
  if(se tenho valor retornarei um Some com o valor) {
    return new Some<String>(valor);
  } else {
    // não tenho valor, ao invés de retornar nulo 
    //e correr o risco do código cliente chamar um método em null, retornarei um None           
    return new None<String>();
  }    
}

renanreismartins

public abstract class Option<T> {
  public abstract boolean hasValue();
  
  public abstract T get();

  public T getOrElse(T alternative) {
    return hasValue() == true ? get() : alternative;
  }
}

renanreismartins

public final class Some<T> extends Option<T> {
  private final T value;

  public Some(T value) { this.value = value; }

  public boolean hasValue() { return true; }
  
  public T get() { return value; }

  @Override

renanreismartins

public final class None<T> extends Option<T> {
  public static class NoneHasNoValue extends RuntimeException {}

  public None() {}

  public boolean hasValue() { return false; }

  public T get() { throw new NoneHasNoValue(); }

  @Override

renanreismartins

@Override
protected void onCreate(Bundle savedInstanceState) {
  ...
  
  GoogleCloudMessaging gcm = GoogleCloudMessaging.getInstance(this);
  String regid = getRegistrationId(context);
  
  if (regid.isEmpty()) {
    registerInBackground();
  }

renanreismartins

private void registerInBackground() {
  new AsyncTask() {
  @Override
  protected String doInBackground(Object[] params) {
      regid = gcm.register(SENDER_ID);
      sendRegistrationIdToBackend(regid);
      storeRegistrationId(context, regid);
      
      ...
  }