Java Beta类代码示例

import com.google.common.annotations.Beta; //导入依赖的package包/类
/**
 * Appends the string representation of each entry in {@code entries}, using the previously
 * configured separator and key-value separator, to {@code appendable}.
 *
 * @since 11.0
 */
@Beta
@CanIgnoreReturnValue
public <A extends Appendable> A appendTo(A appendable, Iterator<? extends Entry<?, ?>> parts)
    throws IOException {
  checkNotNull(appendable);
  if (parts.hasNext()) {
    Entry<?, ?> entry = parts.next();
    appendable.append(joiner.toString(entry.getKey()));
    appendable.append(keyValueSeparator);
    appendable.append(joiner.toString(entry.getValue()));
    while (parts.hasNext()) {
      appendable.append(joiner.separator);
      Entry<?, ?> e = parts.next();
      appendable.append(joiner.toString(e.getKey()));
      appendable.append(keyValueSeparator);
      appendable.append(joiner.toString(e.getValue()));
    }
  }
  return appendable;
}
 

import com.google.common.annotations.Beta; //导入依赖的package包/类
/**
 * Returns a {@link Collector} that accumulates elements into an {@code ImmutableMap} whose keys
 * and values are the result of applying the provided mapping functions to the input elements. The
 * resulting implementation is specialized for enum key types. The returned map and its views will
 * iterate over keys in their enum definition order, not encounter order.
 *
 * <p>If the mapped keys contain duplicates, the values are merged using the specified merging
 * function.
 *
 * @since 21.0
 */
@Beta
public static <T, K extends Enum<K>, V> Collector<T, ?, ImmutableMap<K, V>> toImmutableEnumMap(
    java.util.function.Function<? super T, ? extends K> keyFunction,
    java.util.function.Function<? super T, ? extends V> valueFunction,
    BinaryOperator<V> mergeFunction) {
  checkNotNull(keyFunction);
  checkNotNull(valueFunction);
  checkNotNull(mergeFunction);
  // not UNORDERED because we don't know if mergeFunction is commutative
  return Collector.of(
      () -> new Accumulator<K, V>(mergeFunction),
      (accum, t) -> {
        K key = checkNotNull(keyFunction.apply(t), "Null key for input %s", t);
        V newValue = checkNotNull(valueFunction.apply(t), "Null value for input %s", t);
        accum.put(key, newValue);
      },
      Accumulator::combine,
      Accumulator::toImmutableMap);
}
 

import com.google.common.annotations.Beta; //导入依赖的package包/类
/**
 * Parses the specified string as a double-precision floating point value. The ASCII character
 * {@code '-'} (<code>'&#92;u002D'</code>) is recognized as the minus sign.
 *
 * <p>Unlike {@link Double#parseDouble(String)}, this method returns {@code null} instead of
 * throwing an exception if parsing fails. Valid inputs are exactly those accepted by
 * {@link Double#valueOf(String)}, except that leading and trailing whitespace is not permitted.
 *
 * <p>This implementation is likely to be faster than {@code
 * Double.parseDouble} if many failures are expected.
 *
 * @param string the string representation of a {@code double} value
 * @return the floating point value represented by {@code string}, or {@code null} if
 *     {@code string} has a length of zero or cannot be parsed as a {@code double} value
 * @since 14.0
 */
@Beta
@Nullable
@CheckForNull
@GwtIncompatible // regular expressions
public static Double tryParse(String string) {
  if (FLOATING_POINT_PATTERN.matcher(string).matches()) {
    // TODO(lowasser): could be potentially optimized, but only with
    // extensive testing
    try {
      return Double.parseDouble(string);
    } catch (NumberFormatException e) {
      // Double.parseDouble has changed specs several times, so fall through
      // gracefully
    }
  }
  return null;
}
 

import com.google.common.annotations.Beta; //导入依赖的package包/类
private static void fields() {
  Fields fs1 = Scanner.paths("/io/ytcode/reflect/").scan().classes().fields();

  Fields fs2 =
      fs1.annotatedWith(Beta.class)
          .filter(
              new Predicate<Field>() {
                @Override
                public boolean apply(Field f) {
                  return Modifier.isStatic(f.getModifiers());
                }
              });
  System.out.println(fs2);

  Fields fs3 = fs1.modifiers(Modifier.PUBLIC, Modifier.STATIC);
  System.out.println(fs3);
}
 

import com.google.common.annotations.Beta; //导入依赖的package包/类
/**
 * Reads lines of text from this source, processing each line as it is read using the given
 * {@link LineProcessor processor}. Stops when all lines have been processed or the processor
 * returns {@code false} and returns the result produced by the processor.
 *
 * <p>Like {@link BufferedReader}, this method breaks lines on any of {@code \n}, {@code \r} or
 * {@code \r\n}, does not include the line separator in the lines passed to the {@code processor}
 * and does not consider there to be an extra empty line at the end if the content is terminated
 * with a line separator.
 *
 * @throws IOException if an I/O error occurs in the process of reading from this source or if
 *     {@code processor} throws an {@code IOException}
 * @since 16.0
 */
@Beta
@CanIgnoreReturnValue // some processors won't return a useful result
public <T> T readLines(LineProcessor<T> processor) throws IOException {
  checkNotNull(processor);

  Closer closer = Closer.create();
  try {
    Reader reader = closer.register(openStream());
    return CharStreams.readLines(reader, processor);
  } catch (Throwable e) {
    throw closer.rethrow(e);
  } finally {
    closer.close();
  }
}
 

import com.google.common.annotations.Beta; //导入依赖的package包/类
/**
 * Returns an immutable map instance containing the given entries.
 * Internally, the returned map will be backed by an {@link EnumMap}.
 *
 * <p>The iteration order of the returned map follows the enum's iteration
 * order, not the order in which the elements appear in the given map.
 *
 * @param map the map to make an immutable copy of
 * @return an immutable map containing those entries
 * @since 14.0
 */
@GwtCompatible(serializable = true)
@Beta
public static <K extends Enum<K>, V> ImmutableMap<K, V> immutableEnumMap(
    Map<K, ? extends V> map) {
  if (map instanceof ImmutableEnumMap) {
    @SuppressWarnings("unchecked") // safe covariant cast
    ImmutableEnumMap<K, V> result = (ImmutableEnumMap<K, V>) map;
    return result;
  } else if (map.isEmpty()) {
    return ImmutableMap.of();
  } else {
    for (Map.Entry<K, ? extends V> entry : map.entrySet()) {
      checkNotNull(entry.getKey());
      checkNotNull(entry.getValue());
    }
    return ImmutableEnumMap.asImmutable(new EnumMap<K, V>(map));
  }
}
 

import com.google.common.annotations.Beta; //导入依赖的package包/类
/**
 * Returns a view of the portion of {@code map} whose keys are contained by {@code range}.
 *
 * <p>This method delegates to the appropriate methods of {@link NavigableMap} (namely
 * {@link NavigableMap#subMap(Object, boolean, Object, boolean) subMap()},
 * {@link NavigableMap#tailMap(Object, boolean) tailMap()}, and
 * {@link NavigableMap#headMap(Object, boolean) headMap()}) to actually construct the view.
 * Consult these methods for a full description of the returned view's behavior.
 *
 * <p><b>Warning:</b> {@code Range}s always represent a range of values using the values' natural
 * ordering. {@code NavigableMap} on the other hand can specify a custom ordering via a
 * {@link Comparator}, which can violate the natural ordering. Using this method (or in general
 * using {@code Range}) with unnaturally-ordered maps can lead to unexpected and undefined
 * behavior.
 *
 * @since 20.0
 */
@Beta
@GwtIncompatible // NavigableMap
public static <K extends Comparable<? super K>, V> NavigableMap<K, V> subMap(
    NavigableMap<K, V> map, Range<K> range) {
  if (map.comparator() != null
      && map.comparator() != Ordering.natural()
      && range.hasLowerBound()
      && range.hasUpperBound()) {
    checkArgument(
        map.comparator().compare(range.lowerEndpoint(), range.upperEndpoint()) <= 0,
        "map is using a custom comparator which is inconsistent with the natural ordering.");
  }
  if (range.hasLowerBound() && range.hasUpperBound()) {
    return map.subMap(
        range.lowerEndpoint(),
        range.lowerBoundType() == BoundType.CLOSED,
        range.upperEndpoint(),
        range.upperBoundType() == BoundType.CLOSED);
  } else if (range.hasLowerBound()) {
    return map.tailMap(range.lowerEndpoint(), range.lowerBoundType() == BoundType.CLOSED);
  } else if (range.hasUpperBound()) {
    return map.headMap(range.upperEndpoint(), range.upperBoundType() == BoundType.CLOSED);
  }
  return checkNotNull(map);
}
 

import com.google.common.annotations.Beta; //导入依赖的package包/类
/**
 * Returns a {@code Collector} that accumulates elements into an {@code ImmutableTable}. Each
 * input element is mapped to one cell in the returned table, with the rows, columns, and values
 * generated by applying the specified functions.
 *
 * <p>The returned {@code Collector} will throw a {@code NullPointerException} at collection time
 * if the row, column, or value functions return null on any input.
 *
 * @since 21.0
 */
@Beta
public static <T, R, C, V> Collector<T, ?, ImmutableTable<R, C, V>> toImmutableTable(
    Function<? super T, ? extends R> rowFunction,
    Function<? super T, ? extends C> columnFunction,
    Function<? super T, ? extends V> valueFunction) {
  checkNotNull(rowFunction);
  checkNotNull(columnFunction);
  checkNotNull(valueFunction);
  return Collector.of(
      () -> new ImmutableTable.Builder<R, C, V>(),
      (builder, t) ->
          builder.put(rowFunction.apply(t), columnFunction.apply(t), valueFunction.apply(t)),
      (b1, b2) -> b1.combine(b2),
      b -> b.build());
}
 

import com.google.common.annotations.Beta; //导入依赖的package包/类
/**
 * Returns an immutable map containing the specified entries.  The returned
 * map iterates over entries in the same order as the original iterable.
 *
 * @throws NullPointerException if any key, value, or entry is null
 * @throws IllegalArgumentException if two entries have the same key
 * @since 19.0
 */
@Beta
public static <K, V> ImmutableMap<K, V> copyOf(
    Iterable<? extends Entry<? extends K, ? extends V>> entries) {
  @SuppressWarnings("unchecked") // we'll only be using getKey and getValue, which are covariant
  Entry<K, V>[] entryArray = (Entry<K, V>[]) Iterables.toArray(entries, EMPTY_ENTRY_ARRAY);
  switch (entryArray.length) {
    case 0:
      return of();
    case 1:
      Entry<K, V> onlyEntry = entryArray[0];
      return of(onlyEntry.getKey(), onlyEntry.getValue());
    default:
      /*
       * The current implementation will end up using entryArray directly, though it will write
       * over the (arbitrary, potentially mutable) Entry objects actually stored in entryArray.
       */
      return RegularImmutableMap.fromEntries(entryArray);
  }
}
 

import com.google.common.annotations.Beta; //导入依赖的package包/类
/**
 * Returns a {@link Collector} that accumulates elements into an {@code ImmutableMap} whose keys
 * and values are the result of applying the provided mapping functions to the input elements.
 *
 * <p>If the mapped keys contain duplicates (according to {@link Object#equals(Object)}), the
 * values are merged using the specified merging function. Entries will appear in the encounter
 * order of the first occurrence of the key.
 *
 * @since 21.0
 */
@Beta
public static <T, K, V> Collector<T, ?, ImmutableMap<K, V>> toImmutableMap(
    Function<? super T, ? extends K> keyFunction,
    Function<? super T, ? extends V> valueFunction,
    BinaryOperator<V> mergeFunction) {
  checkNotNull(keyFunction);
  checkNotNull(valueFunction);
  checkNotNull(mergeFunction);
  return Collectors.collectingAndThen(
      Collectors.toMap(keyFunction, valueFunction, mergeFunction, LinkedHashMap::new),
      ImmutableMap::copyOf);
}
 

import com.google.common.annotations.Beta; //导入依赖的package包/类
/**
 * Returns a copy of {@code multiset} as an {@link ImmutableMultiset} whose iteration order is
 * highest count first, with ties broken by the iteration order of the original multiset.
 *
 * @since 11.0
 */
@Beta
public static <E> ImmutableMultiset<E> copyHighestCountFirst(Multiset<E> multiset) {
  List<Entry<E>> sortedEntries =
      Multisets.DECREASING_COUNT_ORDERING.immutableSortedCopy(multiset.entrySet());
  return ImmutableMultiset.copyFromEntries(sortedEntries);
}
 

import com.google.common.annotations.Beta; //导入依赖的package包/类
@Beta
public static <T, K, V> Collector<T, ?, ImmutableSortedMap<K, V>> toImmutableSortedMap(
    Comparator<? super K> comparator,
    Function<? super T, ? extends K> keyFunction,
    Function<? super T, ? extends V> valueFunction,
    BinaryOperator<V> mergeFunction) {
  checkNotNull(comparator);
  checkNotNull(keyFunction);
  checkNotNull(valueFunction);
  checkNotNull(mergeFunction);
  return Collectors.collectingAndThen(
      Collectors.toMap(
          keyFunction, valueFunction, mergeFunction, () -> new TreeMap<K, V>(comparator)),
      ImmutableSortedMap::copyOfSorted);
}
 

import com.google.common.annotations.Beta; //导入依赖的package包/类
/**
 * Returns the largest power of two less than or equal to {@code x}.  This is equivalent to
 * {@code checkedPow(2, log2(x, FLOOR))}.
 *
 * @throws IllegalArgumentException if {@code x <= 0}
 * @since 20.0
 */
@Beta
public static long floorPowerOfTwo(long x) {
  checkPositive("x", x);

  // Long.highestOneBit was buggy on GWT.  We've fixed it, but I'm not certain when the fix will
  // be released.
  return 1L << ((Long.SIZE - 1) - Long.numberOfLeadingZeros(x));
}
 

import com.google.common.annotations.Beta; //导入依赖的package包/类
/**
 * Returns the sum of {@code a} and {@code b} unless it would overflow or underflow in which case
 * {@code Long.MAX_VALUE} or {@code Long.MIN_VALUE} is returned, respectively.
 *
 * @since 20.0
 */
@Beta
public static long saturatedAdd(long a, long b) {
  long naiveSum = a + b;
  if ((a ^ b) < 0 | (a ^ naiveSum) >= 0) {
    // If a and b have different signs or a has the same sign as the result then there was no
    // overflow, return.
    return naiveSum;
  }
  // we did over/under flow, if the sign is negative we should return MAX otherwise MIN
  return Long.MAX_VALUE + ((naiveSum >>> (Long.SIZE - 1)) ^ 1);
}
 

import com.google.common.annotations.Beta; //导入依赖的package包/类
/**
 * Returns a list of delegate futures that correspond to the futures received in the order that
 * they complete. Delegate futures return the same value or throw the same exception as the
 * corresponding input future returns/throws.
 *
 * <p>Cancelling a delegate future has no effect on any input future, since the delegate future
 * does not correspond to a specific input future until the appropriate number of input futures
 * have completed. At that point, it is too late to cancel the input future. The input future's
 * result, which cannot be stored into the cancelled delegate future, is ignored.
 *
 * @since 17.0
 */
@Beta
@GwtIncompatible // TODO
public static <T> ImmutableList<ListenableFuture<T>> inCompletionOrder(
    Iterable<? extends ListenableFuture<? extends T>> futures) {
  // A CLQ may be overkill here. We could save some pointers/memory by synchronizing on an
  // ArrayDeque
  final ConcurrentLinkedQueue<SettableFuture<T>> delegates = Queues.newConcurrentLinkedQueue();
  ImmutableList.Builder<ListenableFuture<T>> listBuilder = ImmutableList.builder();
  // Using SerializingExecutor here will ensure that each CompletionOrderListener executes
  // atomically and therefore that each returned future is guaranteed to be in completion order.
  // N.B. there are some cases where the use of this executor could have possibly surprising
  // effects when input futures finish at approximately the same time _and_ the output futures
  // have directExecutor listeners. In this situation, the listeners may end up running on a
  // different thread than if they were attached to the corresponding input future. We believe
  // this to be a negligible cost since:
  // 1. Using the directExecutor implies that your callback is safe to run on any thread.
  // 2. This would likely only be noticeable if you were doing something expensive or blocking on
  //    a directExecutor listener on one of the output futures which is an antipattern anyway.
  SerializingExecutor executor = new SerializingExecutor(directExecutor());
  for (final ListenableFuture<? extends T> future : futures) {
    SettableFuture<T> delegate = SettableFuture.create();
    // Must make sure to add the delegate to the queue first in case the future is already done
    delegates.add(delegate);
    future.addListener(
        new Runnable() {
          @Override
          public void run() {
            delegates.remove().setFuture(future);
          }
        },
        executor);
    listBuilder.add(delegate);
  }
  return listBuilder.build();
}