collectionutils.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.util.*;

/**
 * Collection of useful static methods for working with Collections. Includes
 * methods to increment counts in maps and cast list/map elements to common types.
 *
 * @author Joseph Smarr ([e-mail])
 */
public class CollectionUtils
{
    /** Private constructor to prevent direct instantiation. */
    private CollectionUtils() { }
    
    /**
     * Adds the given delta to the Integer value stored for the given key in
     * the given Map. Returns whether the entry had to be created (i.e. it wasn't
     * in the map), in which case it's inserted with delta as the initial value.
     * @param map Map from keys to Integer values representing key counts
     * @param key key in map for Integer to increment
     * @param delta amount to change Integer value count by
     * @return whether a new entry for the given key was created in the process (i.e.
     * if it wasn't in the map before).
     */
    public static boolean incrementCount(Map map,Object key,int delta)
    {
        boolean created=false;
        Integer count=(Integer)map.get(key);
        if(count==null)
        {
            count=new Integer(0);
            created=true;
        }
        map.put(key,new Integer(count.intValue()+delta));
        return(created);
    }
    
    /** 
     * Increments the Integer count of the given key in the given Map by 1.
     * @see #incrementCount(Map,String,int)
     */
    public static boolean incrementCount(Map map,Object key)
    {
        return(incrementCount(map,key,1));
    }
    
    // list casting methods
    
    /** Returns <tt>(String)list.get(index)</tt>. */
    public static String getString(List list,int index)
    {
        return((String)list.get(index));
    }
    
    /** Returns <tt>(Integer)list.get(index)</tt>. */
    public static Integer getInteger(List list,int index)
    {
        return((Integer)list.get(index));
    }
    
    /** Returns <tt>((Integer)list.get(index)).intValue()</tt>. */
    public static int getInt(List list,int index)
    {
        return(getInteger(list,index).intValue());
    }
    
    /** Returns <tt>(Double)list.get(index)</tt>. */
    public static Double getDouble(List list,int index)
    {
        return((Double)list.get(index));
    }
    
    /** Returns <tt>((Double)list.get(index)).doubleValue()</tt>. */
    public static double getdouble(List list,int index)
    {
        return(getDouble(list,index).doubleValue());
    }
    
    /** Returns <tt>((Boolean)list.get(index)).booleanValue()</tt>. */
    public static boolean getBoolean(List list,int index)
    {
        return(((Boolean)list.get(index)).booleanValue());
    }    
    
    // map casting methods
        
    /** Returns <tt>(String)map.get(key)</tt>. */
    public static String getString(Map map,Object key)
    {
        return((String)map.get(key));
    }
    
    /** Returns <tt>(Integer)map.get(key)</tt>. */
    public static Integer getInteger(Map map,Object key)
    {
        return((Integer)map.get(key));
    }
    
    /** Returns <tt>((Integer)map.get(key)).intValue()</tt>. */
    public static int getInt(Map list,Object key)
    {
        return(getInteger(list,key).intValue());
    }
    
    /** Returns <tt>(Double)map.get(key)</tt>. */
    public static Double getDouble(Map map,Object key)
    {
        return((Double)map.get(key));
    }
    
    /** Returns <tt>((Double)map.get(key)).doubleValue()</tt>. */
    public static double getdouble(Map map,Object key)
    {
        return(getDouble(map,key).doubleValue());
    }
    
    /** Returns <tt>((Boolean)map.get(key)).booleanValue()</tt>. */
    public static boolean getBoolean(Map map,Object key)
    {
        return(((Boolean)map.get(key)).booleanValue());
    }    
}