EqualsUtil.java

/**
 * Licensed to The Apereo Foundation under one or more contributor license
 * agreements. See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 *
 * The Apereo Foundation licenses this file to you under the Educational
 * Community 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://opensource.org/licenses/ecl2.txt
 *
 * 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 org.opencastproject.util;

import java.util.Iterator;
import java.util.List;
import java.util.Map;

/** Utility function helping to implement equality. */
public final class EqualsUtil {
  private EqualsUtil() {
  }

  /** Check if <code>a</code> and <code>b</code> are equal. Each of them may be null. */
  public static boolean eqObj(Object a, Object b) {
    return (a == b) || (a != null && a.equals(b));
  }

  /** Check if <code>a</code> and <code>b</code> are equal. Each of them may be null. */
  public static boolean eq(Object a, Object b) {
    return (a == b) || (a != null && a.equals(b));
  }

  /** Check if <code>a</code> and <code>b</code> are not equal. Each of them may be null. */
  public static boolean ne(Object a, Object b) {
    return !eq(a, b);
  }

  /** Check if <code>a</code> and <code>b</code> have the same class ({@link Object#getClass()}). Each may be null. */
  public static boolean eqClasses(Object a, Object b) {
    return bothNotNull(a, b) && a.getClass().equals(b.getClass());
  }

  /** Compare the elements of two lists for equality treating the lists as sets. */
  public static boolean eqListUnsorted(List<?> as, List<?> bs) {
    if (as != null && bs != null && as.size() == bs.size()) {
      for (Object a : as) {
        if (!bs.contains(a))
          return false;
      }
      return true;
    } else {
      return eqObj(as, bs);
    }
  }

  /**
   * Compare the elements of two lists one by one.
   *
   * @deprecated use {@link #eqObj(Object, Object)} or {@link java.util.List#equals(Object)}
   */
  public static boolean eqListSorted(List<?> as, List<?> bs) {
    if (as != null && bs != null && as.size() == bs.size()) {
      final Iterator<?> asi = as.iterator();
      final Iterator<?> bsi = bs.iterator();
      while (asi.hasNext() && bsi.hasNext()) {
        if (!asi.next().equals(bsi.next()))
          return false;
      }
      return true;
    } else {
      return eqObj(as, bs);
    }
  }

  /**
   * Compare two maps.
   *
   * @deprecated use {@link #eqObj(Object, Object)} or {@link java.util.Map#equals(Object)}
   */
  public static boolean eqMap(Map<?, ?> as, Map<?, ?> bs) {
    for (Map.Entry<?, ?> ae : as.entrySet()) {
      final Object bv = bs.get(ae.getKey());
      if (bv == null || !eqObj(ae.getValue(), bv))
        return false;
    }
    return true;
  }

  /** Check if both objects are either null or not null. */
  public static boolean bothNullOrNot(Object a, Object b) {
    return !(a == null ^ b == null);
  }

  public static boolean bothNotNull(Object a, Object b) {
    return a != null && b != null;
  }

  public static boolean bothNull(Object a, Object b) {
    return a == null && b == null;
  }

  /**
   * Create a hash code for a list of objects. Each of them may be null.
   * Algorithm adapted from "Programming in Scala, Second Edition", p670.
   */
  public static int hash(Object... as) {
    if (as == null)
      return 0;
    int hash = 0;
    for (Object a : as) {
      if (hash != 0)
        hash = 41 * hash + hash1(a);
      else
        hash = 41 + hash1(a);
    }
    return hash;
  }

  private static int hash1(Object a) {
    return a != null ? a.hashCode() : 0;
  }
}