本文整理了Java中com.annimon.stream.Optional.isPresent()方法的一些代码示例，展示了Optional.isPresent()的具体用法。这些代码示例主要来源于Github/Stackoverflow/Maven等平台，是从一些精选项目中提取出来的代码，具有较强的参考意义，能在一定程度帮忙到你。Optional.isPresent()方法的具体详情如下：
包路径：com.annimon.stream.Optional
类名称：Optional
方法名：isPresent

Optional.isPresent介绍

[英]Checks value present.
[中]检查当前值。

代码示例

代码示例来源：origin: aNNiMON/Lightweight-Stream-API

@Override
public boolean matches(Optional<T> argument) {
  return argument != null && argument.isPresent();
}

代码示例来源：origin: aNNiMON/Lightweight-Stream-API

@Override
protected boolean matchesSafely(Optional<?> optional, Description mismatchDescription) {
  mismatchDescription.appendText("Optional was empty");
  return optional.isPresent();
}

代码示例来源：origin: aNNiMON/Lightweight-Stream-API

/**
 * Performs filtering on inner value if it is present.
 *
 * @param predicate  a predicate function
 * @return this {@code Optional} if the value is present and matches predicate,
 *              otherwise an empty {@code Optional}
 */
public Optional<T> filter(Predicate<? super T> predicate) {
  if (!isPresent()) return this;
  return predicate.test(value) ? this : Optional.<T>empty();
}

代码示例来源：origin: aNNiMON/Lightweight-Stream-API

/**
 * Wraps a value into {@code Stream} if present, otherwise returns an empty {@code Stream}.
 *
 * @return the optional value as a {@code Stream}
 */
@SuppressWarnings("unchecked")
public Stream<T> stream() {
  if (!isPresent()) return Stream.empty();
  return Stream.of(value);
}

代码示例来源：origin: aNNiMON/Lightweight-Stream-API

/**
 * Keeps inner value only if is present and instance of given class.
 *
 * @param <R> a type of instance to select.
 * @param clazz a class which instance should be selected
 * @return an {@code Optional} with value of type class if present, otherwise an empty {@code Optional}
 */
@SuppressWarnings("unchecked")
public <R> Optional<R> select(Class<R> clazz) {
  Objects.requireNonNull(clazz);
  if (!isPresent()) return empty();
  return (Optional<R>) Optional.ofNullable(clazz.isInstance(value) ? value : null);
}

代码示例来源：origin: aNNiMON/Lightweight-Stream-API

/**
 * Invokes mapping function with {@code Optional} result if value is present.
 *
 * @param <U> the type of result value
 * @param mapper  mapping function
 * @return an {@code Optional} with transformed value if present, otherwise an empty {@code Optional}
 */
public <U> Optional<U> flatMap(Function<? super T, Optional<U>> mapper) {
  if (!isPresent()) return empty();
  return Objects.requireNonNull(mapper.apply(value));
}

代码示例来源：origin: aNNiMON/Lightweight-Stream-API

/**
 * Invokes the given mapping function on inner value if present.
 *
 * @param <U> the type of result value
 * @param mapper  mapping function
 * @return an {@code Optional} with transformed value if present,
 *         otherwise an empty {@code Optional}
 * @throws NullPointerException if value is present and
 *         {@code mapper} is {@code null}
 */
public <U> Optional<U> map(Function<? super T, ? extends U> mapper) {
  if (!isPresent()) return empty();
  return Optional.ofNullable(mapper.apply(value));
}

代码示例来源：origin: aNNiMON/Lightweight-Stream-API

/**
 * Invokes mapping function on inner value if present.
 *
 * @param mapper  mapping function
 * @return an {@code OptionalBoolean} with transformed value if present,
 *         otherwise an empty {@code OptionalBoolean}
 * @throws NullPointerException if value is present and
 *         {@code mapper} is {@code null}
 */
public OptionalBoolean mapToBoolean(ToBooleanFunction<? super T> mapper) {
  if (!isPresent()) return OptionalBoolean.empty();
  return OptionalBoolean.of(mapper.applyAsBoolean(value));
}

代码示例来源：origin: aNNiMON/Lightweight-Stream-API

/**
 * Invokes mapping function on inner value if present.
 *
 * @param mapper  mapping function
 * @return an {@code OptionalLong} with transformed value if present,
 *         otherwise an empty {@code OptionalLong}
 * @throws NullPointerException if value is present and
 *         {@code mapper} is {@code null}
 * @since 1.1.4
 */
public OptionalLong mapToLong(ToLongFunction<? super T> mapper) {
  if (!isPresent()) return OptionalLong.empty();
  return OptionalLong.of(mapper.applyAsLong(value));
}

代码示例来源：origin: aNNiMON/Lightweight-Stream-API

/**
 * Invokes the given mapping function on inner value if present.
 *
 * @param mapper  mapping function
 * @return an {@code OptionalInt} with transformed value if present,
 *         otherwise an empty {@code OptionalInt}
 * @throws NullPointerException if value is present and
 *         {@code mapper} is {@code null}
 * @since 1.1.3
 */
public OptionalInt mapToInt(ToIntFunction<? super T> mapper) {
  if (!isPresent()) return OptionalInt.empty();
  return OptionalInt.of(mapper.applyAsInt(value));
}

代码示例来源：origin: aNNiMON/Lightweight-Stream-API

/**
 * Invokes mapping function on inner value if present.
 *
 * @param mapper  mapping function
 * @return an {@code OptionalDouble} with transformed value if present,
 *         otherwise an empty {@code OptionalDouble}
 * @throws NullPointerException if value is present and
 *         {@code mapper} is {@code null}
 * @since 1.1.4
 */
public OptionalDouble mapToDouble(ToDoubleFunction<? super T> mapper) {
  if (!isPresent()) return OptionalDouble.empty();
  return OptionalDouble.of(mapper.applyAsDouble(value));
}

代码示例来源：origin: aNNiMON/Lightweight-Stream-API

/**
 * Returns current {@code Optional} if value is present, otherwise
 * returns an {@code Optional} produced by supplier function.
 *
 * @param supplier  supplier function that produces an {@code Optional} to be returned
 * @return this {@code Optional} if value is present, otherwise
 *         an {@code Optional} produced by supplier function
 * @throws NullPointerException if value is not present and
 *         {@code supplier} or value produced by it is {@code null}
 */
public Optional<T> or(Supplier<Optional<T>> supplier) {
  if (isPresent()) return this;
  Objects.requireNonNull(supplier);
  return Objects.requireNonNull(supplier.get());
}

代码示例来源：origin: aNNiMON/Lightweight-Stream-API

@Test
public void testGetOptional() {
  Optional<Integer> value = Exceptional
      .of(ioExceptionSupplier)
      .getOptional();
  assertFalse(value.isPresent());
}

代码示例来源：origin: aNNiMON/Lightweight-Stream-API

@Test
public void testMapOnEmptyOptional() {
  assertFalse(
      Optional.<Integer>empty()
          .map(UnaryOperator.Util.<Integer>identity())
          .isPresent());
}

代码示例来源：origin: GrossumUA/TAS_Android_Boilerplate

public static <T> Observable<Optional<T>> permute(Optional<Observable<T>> source) {
  if (source.isPresent()) {
    return source.get().map(Optional::ofNullable);
  } else {
    return just(Optional.empty());
  }
}

代码示例来源：origin: GrossumUA/TAS_Android_Boilerplate

public static <T> Observable<T> flatten(Optional<Observable<T>> source) {
  if (source.isPresent()) {
    return source.get();
  } else {
    return empty();
  }
}

代码示例来源：origin: felHR85/UsbSerial

public boolean disconnectDevice(UsbDevice usbDevice){
  Optional<UsbSerialDevice> optionalDevice = Stream.of(serialDevices)
      .filter(p -> usbDevice.getDeviceId() == p.getDeviceId())
      .findSingle();
  if(optionalDevice.isPresent()){
    UsbSerialDevice disconnectedDevice = optionalDevice.get();
    disconnectedDevice.syncClose();
    serialDevices = Utils.removeIf(serialDevices, p -> usbDevice.getDeviceId() == p.getDeviceId());
    return true;
  }
  return false;
}