*   <li>An IPv6 address string with or without brackets, like {@code [2001:db8::1]} or {@code
   *       2001:db8::1}
   * </ul>
   *
   * @throws IllegalArgumentException if the specifier is not valid.
   */
  public static HostSpecifier fromValid(String specifier) {
    // Verify that no port was specified, and strip optional brackets from
    // IPv6 literals.

import org.opensearch.search.aggregations.bucket.filter.FilterAggregationBuilder;
import org.opensearch.search.aggregations.bucket.global.GlobalAggregationBuilder;
import org.opensearch.search.aggregations.bucket.missing.MissingAggregationBuilder;
import org.opensearch.search.aggregations.bucket.range.IpRangeAggregationBuilder;
import org.opensearch.search.aggregations.bucket.sampler.SamplerAggregationBuilder;

 * This API does not try to cover all the requirements out there, just the basic ones, and is intentionally simple.
 * If plugin or extension needs anything more complex feature wise (i.e. HTTP range support or alike) it should
 * probably roll its own.
 * <p>

package com.google.common.base;

import com.google.common.annotations.GwtIncompatible;
import java.io.Serializable;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/** A regex pattern implementation which is backed by the {@link Pattern}. */
@ElementTypesAreNonnullByDefault
@GwtIncompatible
final class JdkPattern extends CommonPattern implements Serializable {
  private final Pattern pattern;

  JdkPattern(Pattern pattern) {

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.HashMap;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Multiset implementation backed by a {@link HashMap}.
 *
 * @author Kevin Bourrillion
 * @author Jared Levy
 * @since 2.0
 */
@GwtCompatible(serializable = true, emulated = true)
@ElementTypesAreNonnullByDefault

import com.google.j2objc.annotations.WeakOuter;
import java.util.Map;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Implementation of ImmutableBiMap backed by a pair of JDK HashMaps, which have smartness
 * protecting against hash flooding.
 */
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault

      unsoundlyCovariantArray[size] = null;
    }
    return array;
  }

  /**
   * Implementation of {@link Collection#toArray(Object[])} for collections backed by an object
   * array. the runtime type of the returned array is that of the specified array. If the collection
   * fits in the specified array, it is returned therein. Otherwise, a new array is allocated with

      default:
        return new RegularImmutableAsList<E>(this, toArray());
    }
  }

  /** If this collection is backed by an array of its elements in insertion order, returns it. */
  Object @Nullable [] internalArray() {
    return null;
  }

  /**
   * If this collection is backed by an array of its elements in insertion order, returns the offset
   * where this collection's elements start.
   */

/**
 * Implementation of ImmutableMap backed by a JDK HashMap, which has smartness protecting against
 * hash flooding.
 */
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
final class JdkBackedImmutableMap<K, V> extends ImmutableMap<K, V> {
  /**
   * Creates an {@code ImmutableMap} backed by a JDK HashMap. Used when probable hash flooding is

import java.util.EnumMap;
import java.util.HashMap;
import java.util.Map;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@code BiMap} backed by an {@code EnumMap} instance for keys-to-values, and a {@code HashMap}
 * instance for values-to-keys. Null keys are not permitted, but null values are. An {@code
 * EnumHashBiMap} and its inverse are both serializable.
 *