AbstractEntry.java

/*
 * Written by Cliff Click and released to the public domain, as explained at
 * http://creativecommons.org/licenses/publicdomain
 */
package org.cliffc.high_scale_lib;

import java.util.*;

/**
 * A simple implementation of {@link java.util.Map.Entry}.
 * Does not implement {@link java.util.Map.Entry.setValue}, that is done by users of the class.
 *
 * @since 1.5
 * @author Cliff Click
 * @param <TypeK> the type of keys maintained by this map
 * @param <TypeV> the type of mapped values
 */
abstract class AbstractEntry<TypeK, TypeV> implements Map.Entry<TypeK, TypeV> {

  /** Strongly typed key */
  protected final TypeK _key;
  /** Strongly typed value */
  protected TypeV _val;

  public AbstractEntry(final TypeK key, final TypeV val) {
    _key = key;
    _val = val;
  }

  public AbstractEntry(final Map.Entry<TypeK, TypeV> e) {
    _key = e.getKey();
    _val = e.getValue();
  }

  /** Return "key=val" string */
  @Override
  public String toString() {
    return _key + "=" + _val;
  }

  /** Return key */
  @Override
  public TypeK getKey() {
    return _key;
  }

  /** Return val */
  @Override
  public TypeV getValue() {
    return _val;
  }

  /** Equal if the underlying key & value are equal */
  @Override
  public boolean equals(final Object o) {
    if (!(o instanceof Map.Entry)) {
      return false;
    }
    final Map.Entry e = (Map.Entry) o;
    return eq(_key, e.getKey()) && eq(_val, e.getValue());
  }

  /** Compute <code>"key.hashCode() ^ val.hashCode()"</code> */
  @Override
  public int hashCode() {
    return ((_key == null) ? 0 : _key.hashCode())
            ^ ((_val == null) ? 0 : _val.hashCode());
  }

  private static boolean eq(final Object o1, final Object o2) {
    return (o1 == null ? o2 == null : o1.equals(o2));
  }
}