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Java implementation of some of the core utilities from Scala
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/**
 * Copyright 2015 Peter Nerg
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of the License at
 *
 * 
http://www.apache.org/licenses/LICENSE-2.0
 *
 * 
Unless required by applicable law or agreed to in writing, software distributed under the
 * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
 * express or implied. See the License for the specific language governing permissions and
 * limitations under the License.
 */
package javascalautils;

import java.io.Serializable;

/**
 * Represents the type scala.Unit. 

 * The usage of Unit is for situations where one returns types such as {@link Try} or {@link
 * javascalautils.concurrent.Future Future} that are not meant to hold a value. 

 * E.g.
 *
 * 
 * 
 * Try<Unit> deleteSynchronous(String id)
 * Future<Unit> deleteAsynchronous(String id)
 * 
 * 
 *
 * The example illustrates deleting something but the only thing we care of is if the operation was
 * successful.

 * This becomes very apparent with the asynchronous method. In that case we only care if the
 * operation is finished and successful.

 * One can of course return dummy objects/values but providing Unit is more concise as it clearly
 * marks a non-value. 

 * Instead of creating new instances it is recommended to use the {@link #Instance singleton}
 * instance.
 *
 * @author Peter Nerg
 * @since 1.6
 */
public final class Unit implements Serializable {

  /**
   * Static singleton representing the Unit.
   *
   * @since 1.7
   */
  public static final Unit Instance = new Unit();

  private static final long serialVersionUID = 75L;

  /**
   * Always returns 69.
   *
   * @since 1.7
   * @return Always 69
   */
  @Override
  public int hashCode() {
    return 69;
  }

  /**
   * Simply compares the provided object to see if it is an instance of {@link Unit}.
   *
   * @param obj The object to compare to
   * @since 1.7
   */
  @Override
  public boolean equals(Object obj) {
    if (this == obj) {
      return true;
    }
    if (obj == null) {
      return false;
    }
    return getClass() == obj.getClass();
  }

  /**
   * Always returns the string Unit
   *
   * @return The string Unit
   * @since 1.7
   */
  @Override
  public String toString() {
    return "Unit";
  }
}