The wee library

No extra dependencies, just a few helper objects for your daily Java needs

Lazy

Helper object for deferring expensive and probably optional computations

Lazy<Rock> rock = Lazy.of(() -> pushTheRockUpTheMountain());

if (sysyphus.isntTired()) {
  rock.get();
}

Cached

Mostly lazy but with occasional bursts of diligence

Helper object for caching values

Supplier<Double> randomDoubleSupplier = spyRandomSupplier();

Duration retentionPeriod = Duration.ofMillis(10);
Cached<Double> cachedRandomDouble =
    Cached.of(randomDoubleSupplier)
        .retainingFor(retentionPeriod);

cachedRandomDouble.get();
waitFor(retentionPeriod.plus(10, ChronoUnit.MILLIS));
cachedRandomDouble.get();

verify(randomDoubleSupplier, times(TWICE)).get();

Recoverable

Useful for operations for which we can provide fallbacks in case of failures

AtomicBoolean executionFlag = new AtomicBoolean(false);

Recoverable<String> serviceHostnameFetcher =  
    Recoverable
      .of(() -> pingAndReturnFirstAvailableNode())
      .recoverIf(SocketException.class, () -> getLocalHostname())
      .finallyDo(() -> executionFlag.set(true))
      .go();

assertTrue(serviceHostnameFetcher.isExecuted());
assertTrue(executionFlag.get());
assertTrue(serviceHostnameFetcher.getExecutionTimestamp().isPresent());
assertTrue(serviceHostnameFetcher.isSuccessful());
assertTrue(serviceHostnameFetcher.getRecoveryCause().isPresent());
assertFalse(serviceHostnameFetcher.getFailureCause().isPresent());
assertEquals(SocketException.class, serviceHostnameFetcher.getRecoveryCause().get().getClass());
assertEquals(getLocalHostname(), serviceHostnameFetcher.getResult());

RepeatingAttempt

Useful for polling or retrying

RepeatingAttempt<Integer> progressCheck =
    RepeatingAttempt
      .of(() -> {
        int progress = pollProgress();
    
        return progress; 
      })
      .until((progress) -> progress == 100) //when to stop attempting
      .fixedDelay(300) //300 millis between attempts
      .abortingAfter(10) //aborting after 10 attempts
      .go();

assertTrue(progressCheck.isStarted());
assertTrue(progressCheck.isFinished());

//In case we did reach the result we were attempting to get
assertTrue(progressCheck.isSuccessful()); 
assertTrue(progressCheck.getResult().isPresent());
assertEquals(100, progressCheck.getResult().get());

Exceptions

For building exceptions with templated messages

//Create an Exception object
IllegalStateException forSafeKeeping = 
  Exceptions
    .create(IllegalStateException.class)
    .withMessage("Here's an exception that's {} millis old", System.currentTimeMillis())
    .build();

//Or create and throw it
Exception cause = new UnsupportedOperationException("Oops...");
String panicDegree = Math.random() > 0.5 ? " very " : " ";
Exceptions
  .create(IllegalStateException.class)
  .withCause(cause)
  .withMessage("Encountered a{}nasty exception", panicDegree)
  .buildAndThrow();

Strings

Facade for creating and printing templated strings.

String adjective = "wonderful";
String punctuation = Math.random() > 0.5 ? "!" : ".";
String template = "This is a {} example {}";

String result = Strings.create(template, adjective, punctuation);
assertEquals("This is a wonderful example " + punctuation, result);

Strings.print().stdout().println(template, adjective, punctuation);

PrintStream somePrintStream = createAnExcellentPrintStream();
Strings.print().to(somePrintStream).println(template, adjective, punctuation);

//Also, the StringPrinter's methods are chainable
Strings.print().stdout()
  .println("Right now, at {}", System.currentTimeMillis())
  .println("We are pretty bored with the whole situation")
  .println("One can only hope that something {}ly entertaining will happen", adjective);

Also for checking if a string is empty/null or not.

assertTrue(Strings.isEmpty(null));
assertTrue(Strings.isEmpty(""));
assertFalse(Strings.isEmpty(" ");

assertFalse(Strings.isNotEmpty(null));
assertFalse(Strings.isNotEmpty(""))
assertTrue(Strings.isNotEmpty(" "))

Classes

Facade for everything related to classes. At the moment, can help you only with fetching a class's simpleName wrapped in the ClassName object which implements the CharSequence interface (so it's ready to print or compare)

Object someObject = UUID.randomUUID();
ClassName className = Classes.name(someObject);
assertTrue("UUID".equals(className));