arrayutils.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;

/**
 * Static utility methods for operating on arrays.
 *
 * @author  Huy Nguyen ([e-mail])
 */
import java.lang.reflect.*;

public class ArrayUtils
{    
    /** Should not be instantiated */
    protected ArrayUtils(){}
    
    /** Removes the element at the specified index from the array, and returns
     *  a new array containing the remaining elements.  If <tt>index</tt> is invalid,
     *  returns <tt>array</tt> unchanged.
     */
    public static double[] removeAt(double[] array, int index) {
        if(array==null) return null;
        if(index<0 || index>=array.length) return array;
        
        double[] retVal=new double[array.length-1];
        for(int i=0; i<array.length; i++) {
            if(i<index) retVal[i]=array[i];
            else if(i>index) retVal[i-1]=array[i];
        }
        return retVal;
    }     
    
    /** Removes the element at the specified index from the array, and returns
     *  a new array containing the remaining elements.  If <tt>index</tt> is invalid,
     *  returns <tt>array</tt> unchanged.  Uses reflection to determine the type
     *  of the array and returns an array of the appropriate type.
     */
    public static Object[] removeAt(Object[] array, int index) {
        if(array==null) return null;
        if(index<0 || index>=array.length) return array;
        
        Object[] retVal=(Object[])Array.newInstance(array[0].getClass(),array.length-1);
        for(int i=0; i<array.length; i++) {
            if(i<index) retVal[i]=array[i];
            else if(i>index) retVal[i-1]=array[i];
        }
        return retVal;
    }    
    
    /** For internal debugging purposes only */
    public static void main(String[] args) {
        String[] strings=new String[]{"a","b","c"};
        strings=(String[])ArrayUtils.removeAt(strings,2);
        for(int i=0; i<strings.length; i++) {
            System.err.println(strings[i]);
        }
    }
}