mapentry.java

实现数据库的storage manager 功能

/*
 * Copyright (c) 2000-2004, Rickard C鰏ter, Martin Svensson
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 * 
 * Redistributions of source code must retain the above copyright notice, 
 * this list of conditions and the following disclaimer. 
 * Redistributions in binary form must reproduce the above copyright notice, 
 * this list of conditions and the following disclaimer in the documentation 
 * and/or other materials provided with the distribution. 
 * Neither the name of SICS nor the names of its contributors 
 * may be used to endorse or promote products derived from this software 
 * without specific prior written permission. 
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
 * POSSIBILITY OF SUCH DAMAGE.
 *
 *
 */

package com.mellowtech.disc;

import java.util.*;

/**
 * Utility class to create that implements the Map.Entry interface. Useful
 * for iterating over collections.
 *
 * @author Martin Svensson
 * @version 1.0
 */
public class MapEntry implements Map.Entry{

  /**
   * The entry key
   *
   */
  protected Object k;
  
  /**
   * The entry value
   *
   */
  protected Object v;
  
  /**
   * Creates a new <code>MapEntry</code> instance.
   *
   */
  public MapEntry(){
    ;
  }
  
  /**
   * First compare the keys and if those are equal compre the values
   *
   * @param o an object to compare with
   * @return true if both the key and value are equal
   */
  public boolean equals(Object o){
    Map.Entry e2 = (Map.Entry) o;
    return (this.getKey()==null ?
	    e2.getKey()==null : this.getKey().equals(e2.getKey()))  &&
      (this.getValue()==null ?
       e2.getValue()==null : this.getValue().equals(e2.getValue()));
  }
  
  /**
   * Get the entry key
   *
   * @return a key
   */
  public Object getKey(){
    return k;
  }
  /**
   * Get the entry value
   *
   * @return a value
   */
  public Object getValue(){ 
    return v;
  }

  /**
   * Set key for this entry
   *
   * @param k the key
   */
  public void setKey(Object k){
    this.k = k;
  }
  /**
   * Set the value for this entry
   *
   * @param value the value
   */
  public Object setValue(Object v){ 
    this.v = v;
    return this.v;
  }
  
  /**
   * Calculates hashCode value as follows.
   * <pre>
   *   return (this.getKey()==null   ? 0 : this.getKey().hashCode()) ^
   *    (this.getValue()==null ? 0 : this.getValue().hashCode());
   * </pre>
   *
   * @return hashCode
   */
  public int hashCode(){
    return (this.getKey()==null   ? 0 : this.getKey().hashCode()) ^
      (this.getValue()==null ? 0 : this.getValue().hashCode());
  }
  
  /**
   * Describe <code>toString</code> method here.
   *
   * @return a <code>String</code> value
   */
  public String toString() {
    return "key=" + getKey() + "\tvalue=" + getValue();
  }
}