pair.java

Standord Classifier实现了一个基于Java的最大熵分类器。用于模式识别

package edu.stanford.nlp.util;

import java.io.Serializable;
import java.io.DataInputStream;
import java.io.DataOutputStream;

/**
 *  Pair: A Class for holding a pair of objects.
 *
 *  @author Dan Klein
 *  @author Christopher Manning (added stuff from Kristina's, rounded out)
 *  @version 2002/08/25
 */
public class Pair implements Comparable, Serializable {

  /** Direct access is deprecated.  Use first().
   *  @serial
   */
  public Object first;

  /** Direct access is deprecated.  Use second().
   *  @serial
   */
  public Object second;
  
  public Pair() {
    // first = null; second = null; -- default initialization
  }

  public Pair(Object first, Object second) {
    this.first = first;
    this.second = second;
  }
  
  public Object first() {
    return first;
  }

  public Object second() {
    return second;
  }

  public String toString() {
    return "("+first+","+second+")";
  }
  
  public boolean equals(Object o) {
    if (o instanceof Pair) {
      Pair p = (Pair) o;
      return (first == null ? p.first == null : first.equals(p.first)) &&
	     (second == null ? p.second == null : second.equals(p.second));
    } else {
      return false;
    }
  }
  
  public int hashCode() {
    return (((first == null) ? 0 : first.hashCode()) << 16) ^ 
	((second == null) ? 0: second.hashCode());
  }
  
  /** Read a string representation of a Pair from a DataStream.
   *  This might not work correctly unless the pair of objects are of type
   *  <code>String</code>.
   */
  public void read(DataInputStream in) {
    try {
      first = in.readUTF();
      second = in.readUTF();
    } catch(Exception e) {
      e.printStackTrace();
    }
  }

  /** Write a string representation of a Pair from a DataStream.
   *  The <code>toString()</code> method is called on each of the pair
   *  of objects and a <code>String</code> representation is written.
   *  This might not allow one to recover the pair of objects unless they 
   *  are of type <code>String</code>.
   */
  public void save(DataOutputStream out) {
    try {
      out.writeUTF(first.toString());
      out.writeUTF(second.toString());
    } catch(Exception e) {
      e.printStackTrace();
    }
  }

  /**
   * Compares this <code>Pair</code> to another object.
   * If the object is a <code>Pair</code>, this function will work providing 
   * the elements of the <code>Pair</code> are themselves comparable.
   * It will then return a value based on the pair of objects, where
   * <code>p &gt; q iff p.first() &gt; q.first() || 
   *      (p.first().equals(q.first()) && p.second() &gt; q.second())</code>.
   * If the other object is not a <code>Pair</code>, it throws a
   * <code>ClassCastException</code>.
   *
   * @param   o the <code>Object</code> to be compared.
   * @return  the value <code>0</code> if the argument is a 
   * <code>Pair</code> equal to this <code>Pair</code>; a value less than
   * <code>0</code> if the argument is a <code>Pair</code> 
   * greater than this <code>Pair</code>; and a value 
   * greater than <code>0</code> if the argument is a 
   * <code>Pair</code> less than this <code>Pair</code>.
   * @exception <code>ClassCastException</code> if the argument is not a
   *  <code>Pair</code>.
   * @see     java.lang.Comparable
   */
  public int compareTo(Object o) {
    Pair another = (Pair) o;
    int comp = ((Comparable) first()).compareTo(another.first());
    if (comp != 0) {
      return comp;
    } else {
      return ((Comparable) second()).compareTo(another.second());
    }
  }

  /** use serialVersionUID for cross version serialization compatibility */
  private static final long serialVersionUID = 1360822168806852920L;

}