Java源码分析:Guava之不可变集合ImmutableMap的源码分析

public static final  Map<String,String> dayMap= new HashMap<>();
static {
    dayMap.put("Monday","今天上英语课");
    dayMap.put("Tuesday","今天上语文课");
    dayMap.put("Wednesday","今天上数学课");
    dayMap.put("Thursday","今天上音乐课");
    dayMap.put("Sunday","今天上编程课");
    ......
}

public static final  Map<String,String> dayMap = ImmutableMap.<String, String>builder()
    .put("Monday","今天上英语课")
    .put("Tuesday","今天上语文课")
    .put("Wednesday","今天上数学课")
    .put("Thursday","今天上音乐课")
    .put("Sunday","今天上编程课")
    .build();

public abstract class ImmutableMap<K, V> implements Map<K, V>, Serializable {}

/**
 * Returns a new builder. The generated builder is equivalent to the builder
 * created by the {@link Builder} constructor.
 */
public static <K, V> Builder<K, V> builder() {
  return new Builder<K, V>();
}

public <T> T method(T t)

public static class Builder<K, V> {
    Comparator<? super V> valueComparator;
    ImmutableMapEntry<K, V>[] entries;
    int size;
    boolean entriesUsed;
   public Builder() {
      this(ImmutableCollection.Builder.DEFAULT_INITIAL_CAPACITY);
    }
    Builder(int initialCapacity) {
      this.entries = new ImmutableMapEntry[initialCapacity];
      this.size = 0;
      this.entriesUsed = false;
    }
    ......
}

class ImmutableMapEntry<K, V> extends ImmutableEntry<K, V> {
  static <K, V> ImmutableMapEntry<K, V>[] createEntryArray(int size) {
    return new ImmutableMapEntry[size];
  }
  ImmutableMapEntry(K key, V value) {
    super(key, value);
    checkEntryNotNull(key, value);
  }
}

static void checkEntryNotNull(Object key, Object value) {
  if (key == null) {
    throw new NullPointerException("null key in entry: null=" + value);
  } else if (value == null) {
    throw new NullPointerException("null value in entry: " + key + "=null");
  }
}

class ImmutableEntry<K, V> extends AbstractMapEntry<K, V> implements Serializable {
  final K key;
  final V value;
  ......
}

public Builder<K, V> put(K key, V value) {
  ensureCapacity(size + 1); 
  ImmutableMapEntry<K, V> entry = entryOf(key, value);
  // don't inline this: we want to fail atomically if key or value is null
  entries[size++] = entry;
  return this;
}

private void ensureCapacity(int minCapacity) {
  if (minCapacity > entries.length) {
    entries =
        Arrays.copyOf(
            entries, ImmutableCollection.Builder.expandedCapacity(entries.length, minCapacity));
    entriesUsed = false;
  }
}

static <K, V> ImmutableMapEntry<K, V> entryOf(K key, V value) {
    return new ImmutableMapEntry<K, V>(key, value);
  }

ImmutableMap.<String, String>builder()
    .put("Monday","今天上英语课")
    ......
    .build();

public ImmutableMap<K, V> build() {
  switch (size) {
    case 0:
      return of();
    case 1:
      return  new SingletonImmutableBiMap<K, V>(k1, v1);
    default:
      return  new RegularImmutableMap<K, V>(entries, table, mask);
  }
}

final class SingletonImmutableBiMap<K, V> extends ImmutableBiMap<K, V> {
  final transient K singleKey;
  final transient V singleValue;
  ......
}

final class RegularImmutableMap<K, V> extends ImmutableMap<K, V> {
  // entries in insertion order
  private final transient Entry<K, V>[] entries;
  // array of linked lists of entries
  private final transient ImmutableMapEntry<K, V>[] table;
  // 'and' with an int to get a table index
  private final transient int mask;
  ......
}

/**
 * Guaranteed to throw an exception and leave the map unmodified.
 *
 * @throws UnsupportedOperationException always
 * @deprecated Unsupported operation.
 */
@CanIgnoreReturnValue
@Deprecated
@Override
public final V put(K k, V v) {
  throw new UnsupportedOperationException();
}