OCP - Before Exam

double d = 1.0;

DoubleToIntFunction f1 = x -> 1;

f1.applyAsInt(d);

Accepts a double and returns an int (implied by the name applyAsInt)

Turning one parameter into a value of a potentially different type and returning it

applyAsDouble

applyAsInt

applyAsLong

Check for compatibility! Years, Months, Week and Days do not work on LocalTime and Hours, Minutes, Seconds and Nonos do not work on LocalDate!

It is useful for multi-level reduction.

Map<City, Set<String>> lastNamesByCity = people.stream()
     .collect(
            groupingBy(Person::getCity,
               mapping(Person::getLastName, toSet())));

ZoneId zone = ZoneId.of("US/Easter");
ZonedDateTime zone = ZonedDateTime.of(2019, 1, 20, 6, 15, 30, 200, zone); # Last Parameter
 

There isn't an option to pass the Month-Enum!

PT24H

PT stands for Period of Time (=Duration). 24 Hours are printed but minutes and seconds are omitted (empty)

An Instant represents a specific moment in time in the GMT time szone.

aZonedDateTime.toInstant();
Instant.now()

You can only add Days, Hours but no weeks and years.
eg. instant.plus(1, ChronoUnit.WEEKS) throws an exception

The timeZone offset changes, eg:

2016-03-13T01:30-05:00[US/Eastern]

2016-03-13T03:30-04:00[US/Eastern]

By extending the LsitResourceBundle

• Always look for the Java Class first, then the property file
• Drop one thing at a time, if there are no matches, strting with the coutnry and then the language
• Default locale and default resource bulde come last

java.text

Not everything is compatible, eg DateTimeFormatter.ofLocalizedTime cannot be used with a LocalDate

Used when converting a String to a number.

IT IS CHECKED!

Yes (extends IOException)

No

• It is ilegal to declare a subclass exception in a chatch block that is lower down in the list than a superclass
• you cannot catch a checked exception type that cannot potentially be thrown by the try clause

It depends on how the try block endend:

• Try-block ended normally: The exception from the close method is thrown and must either be handeled in a catch block or by the caller (checked exceptions must be declared, of course)
• Try-block ended with an exception: The exception from the close method is added as a suppressed exception to the one from the try-block.

It is a short for the following code to prevent duplicates. Java can infer the specific Exception from the method signature

public void rerhrowing() throws SQLException, DateTimeParseException {
  try {
    parseData();
  } catch (SQLException | DateTimeParseException e) {
    System.err.println(e);
    throw e;
  }
}

No

It declares the checked InterruptedException which must be handeled

It is important to call the shutdown() method. A thread executor creates a non-demon thread on the first task that is executed, so failing to call shutdown will result in you application never terminating.

Callable can return a value and allows a throws declaration of Exception

@FunctionalInterface Callable<V> { V call() throws Exception;}

@FunctionalInterface Runnable { void run()}

• Monitor using the synchronized keyword = Locking
• Atomic clases that provide atomic operations

The Blocking versions offer additional methods that will wait for a specific amount of time to complete an operation:

eg. boolean offer(E e, long timeout, TimeUnit unit) throws InterruptedException -> Returns false on timeout

eg. E poll(long timeout, TimeUnit unit) throws InterruptedException -> Returns null on timeout

Seria streams are ordered whereas parallel streams are not necessarily

1. Create a ForkJoinTask
   • ForkJoinTask<?> task = new MyActionOrTask(...);
2. Create the ForkJoinPool
   • ForkJoinPool pool = new ForkJoinPool();
3. Start the ForkJoinTask
   • pool.invoke(action)
   • Object result = pool.invoke(task);

No

By wrapping it with a InputStreamReader

They write formatted representations of Java objects to a binary stream

Yes

When the readLine() method returns null or or read() returns -1

Catch the EOFException!