Present.java

/*
 * Copyright (C) 2015 Open Whisper Systems
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

package org.anhonesteffort.flock.util.guava;

import static org.anhonesteffort.flock.util.guava.Preconditions.checkNotNull;

import java.util.Collections;
import java.util.Set;

/**
 * Implementation of an {@link Optional} containing a reference.
 */

final class Present<T> extends Optional<T> {
  private final T reference;

  Present(T reference) {
    this.reference = reference;
  }

  @Override public boolean isPresent() {
    return true;
  }

  @Override public T get() {
    return reference;
  }

  @Override public T or(T defaultValue) {
    checkNotNull(defaultValue, "use orNull() instead of or(null)");
    return reference;
  }

  @Override public Optional<T> or(Optional<? extends T> secondChoice) {
    checkNotNull(secondChoice);
    return this;
  }

  @Override public T or(Supplier<? extends T> supplier) {
    checkNotNull(supplier);
    return reference;
  }

  @Override public T orNull() {
    return reference;
  }

  @Override public Set<T> asSet() {
    return Collections.singleton(reference);
  }
  
  @Override public <V> Optional<V> transform(Function<? super T, V> function) {
    return new Present<V>(checkNotNull(function.apply(reference),
        "Transformation function cannot return null."));
  }

  @Override public boolean equals(Object object) {
    if (object instanceof Present) {
      Present<?> other = (Present<?>) object;
      return reference.equals(other.reference);
    }
    return false;
  }

  @Override public int hashCode() {
    return 0x598df91c + reference.hashCode();
  }

  @Override public String toString() {
    return "Optional.of(" + reference + ")";
  }

  private static final long serialVersionUID = 0;
}