mergesort.java

java jtable功能的实现

package view;

/*
 * %W% %E%
 *
 * Copyright 1997, 1998 Sun Microsystems, Inc. All Rights Reserved.
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 * 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. 
 *   
 * - Redistribution in binary form must reproduce the above
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 *   provided with the distribution. 
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 * Neither the name of Sun Microsystems, Inc. or the names of
 * contributors may be used to endorse or promote products derived
 * from this software without specific prior written permission.  
 * 
 * This software is provided "AS IS," without a warranty of any
 * kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND
 * WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY
 * EXCLUDED. SUN AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY
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/**
 * An implementation of MergeSort, needs to be subclassed to provide a
 * comparator.
 * 
 * @version %I% %G%
 * 
 * @author Scott Violet
 */
public abstract class MergeSort extends Object {
	protected Object toSort[];

	protected Object swapSpace[];

	public void sort(Object array[]) {
		if (array != null && array.length > 1) {
			int maxLength;

			maxLength = array.length;
			swapSpace = new Object[maxLength];
			toSort = array;
			this.mergeSort(0, maxLength - 1);
			swapSpace = null;
			toSort = null;
		}
	}

	public abstract int compareElementsAt(int beginLoc, int endLoc);

	protected void mergeSort(int begin, int end) {
		if (begin != end) {
			int mid;

			mid = (begin + end) / 2;
			this.mergeSort(begin, mid);
			this.mergeSort(mid + 1, end);
			this.merge(begin, mid, end);
		}
	}

	protected void merge(int begin, int middle, int end) {
		int firstHalf, secondHalf, count;

		firstHalf = count = begin;
		secondHalf = middle + 1;
		while ((firstHalf <= middle) && (secondHalf <= end)) {
			if (this.compareElementsAt(secondHalf, firstHalf) < 0)
				swapSpace[count++] = toSort[secondHalf++];
			else
				swapSpace[count++] = toSort[firstHalf++];
		}
		if (firstHalf <= middle) {
			while (firstHalf <= middle)
				swapSpace[count++] = toSort[firstHalf++];
		} else {
			while (secondHalf <= end)
				swapSpace[count++] = toSort[secondHalf++];
		}
		for (count = begin; count <= end; count++)
			toSort[count] = swapSpace[count];
	}
}