Class Primitives

corpus/java/training/guava/primitives/Primitives.java:33–139

Contains static utility methods pertaining to primitive types and their corresponding wrapper types. @author Kevin Bourrillion @since 1.0

 * @since 1.0
 */
@GwtIncompatible
public final class Primitives {
  private Primitives() {}

  /** A map from primitive types to their corresponding wrapper types. */
  private static final Map<Class<?>, Class<?>> PRIMITIVE_TO_WRAPPER_TYPE;

  /** A map from wrapper types to their corresponding primitive types. */
  private static final Map<Class<?>, Class<?>> WRAPPER_TO_PRIMITIVE_TYPE;

  // Sad that we can't use a BiMap. :(

  static {
    Map<Class<?>, Class<?>> primToWrap = new HashMap<Class<?>, Class<?>>(16);
    Map<Class<?>, Class<?>> wrapToPrim = new HashMap<Class<?>, Class<?>>(16);

    add(primToWrap, wrapToPrim, boolean.class, Boolean.class);
    add(primToWrap, wrapToPrim, byte.class, Byte.class);
    add(primToWrap, wrapToPrim, char.class, Character.class);
    add(primToWrap, wrapToPrim, double.class, Double.class);
    add(primToWrap, wrapToPrim, float.class, Float.class);
    add(primToWrap, wrapToPrim, int.class, Integer.class);
    add(primToWrap, wrapToPrim, long.class, Long.class);
    add(primToWrap, wrapToPrim, short.class, Short.class);
    add(primToWrap, wrapToPrim, void.class, Void.class);

    PRIMITIVE_TO_WRAPPER_TYPE = Collections.unmodifiableMap(primToWrap);
    WRAPPER_TO_PRIMITIVE_TYPE = Collections.unmodifiableMap(wrapToPrim);
  }

  private static void add(
      Map<Class<?>, Class<?>> forward,
      Map<Class<?>, Class<?>> backward,
      Class<?> key,
      Class<?> value) {
    forward.put(key, value);
    backward.put(value, key);
  }

  /**
   * Returns an immutable set of all nine primitive types (including {@code
   * void}). Note that a simpler way to test whether a {@code Class} instance is a member of this
   * set is to call {@link Class#isPrimitive}.
   *
   * @since 3.0
   */
  public static Set<Class<?>> allPrimitiveTypes() {
    return PRIMITIVE_TO_WRAPPER_TYPE.keySet();
  }

  /**
   * Returns an immutable set of all nine primitive-wrapper types (including {@link Void}).
   *
   * @since 3.0
   */
  public static Set<Class<?>> allWrapperTypes() {
    return WRAPPER_TO_PRIMITIVE_TYPE.keySet();
  }