import java.util.AbstractMap;
import java.util.AbstractMap.SimpleImmutableEntry;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.NavigableMap;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.function.BiFunction;
import org.jspecify.annotations.Nullable;

/**

 * under the License.
 */
package org.apache.maven.settings.io;

import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.io.Writer;
import java.util.Map;

import org.apache.maven.settings.Settings;

/**
 * Handles serialization of settings into some kind of textual format like XML.
 *

  static <K extends Enum<K>, V> ImmutableMap<K, V> asImmutable(EnumMap<K, V> map) {
    switch (map.size()) {
      case 0:
        return ImmutableMap.of();
      case 1:
        Entry<K, V> entry = getOnlyElement(map.entrySet());
        return ImmutableMap.of(entry.getKey(), entry.getValue());
      default:
        return new ImmutableEnumMap<>(map);
    }
  }

  private final transient EnumMap<K, V> delegate;

  private transient volatile @Nullable CacheEntry<K, V> cacheEntry1;
  private transient volatile @Nullable CacheEntry<K, V> cacheEntry2;

  MapRetrievalCache(Map<K, V> backingMap) {
    super(backingMap);
  }

  @SuppressWarnings("unchecked") // Safe because we only cast if key is found in map.
  @Override
  @Nullable V get(Object key) {
    checkNotNull(key);
    V value = getIfCached(key);
    if (value != null) {
      return value;

    private static final String EXPRESSION_DOCO_ROOTPATH = "META-INF/maven/plugin-expressions/";

    private static Map<String, Expression> expressionDocumentation;

    public static Map<String, Expression> load() throws ExpressionDocumentationException {
        if (expressionDocumentation == null) {
            expressionDocumentation = new HashMap<>();

import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

class Graph {
    private enum DfsState {
        VISITING,
        VISITED
    }

    final Map<String, Vertex> vertices = new LinkedHashMap<>();

    public Vertex getVertex(String id) {
        return vertices.get(id);
    }

public synchronized class CollectionUtils { public void CollectionUtils(); public static java.util.Map mergeMaps(java.util.Map, java.util.Map); public static java.util.Map mergeMaps(java.util.Map[]); public static java.util.Collection intersection(java.util.Collection, java.util.Collection); public static java.util.Collection subtract(java.util.Collection, java.util.Collection); public static java.util.Map getCardinalityMap(java.util.Collection); public static java.util.List iteratorToList(java.util.Iterator);...

     */
    @Nullable
    String value();

    /**
     * Returns an immutable map of all attributes defined on this XML node.
     *
     * @return map of attribute names to values, never {@code null}
     */
    @Nonnull
    Map<String, String> attributes();

    /**
     * Returns the value of a specific attribute.
     *

import com.google.common.collect.testing.TestSetGenerator;
import com.google.common.collect.testing.TestSubjectGenerator;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**

    cache.put(10, 20);

    Map<Integer, Integer> map = cache.getAll(ImmutableList.of(10, 20, 30, 54, 443, 1));

    assertThat(map).containsEntry(10, 20);
    assertThat(map).containsEntry(20, 0);
    assertThat(map).containsEntry(30, 1);
    assertThat(map).containsEntry(54, 2);
    assertThat(map).containsEntry(443, 3);
    assertThat(map).containsEntry(1, 4);
    assertThat(cache.get(6)).isEqualTo(5);