valuenumberfactory.java

一个查找java程序里bug的程序的源代码,该程序本身也是java写的,对提高java编程水平很有用

/*
 * Bytecode Analysis Framework
 * Copyright (C) 2003,2004 University of Maryland
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package edu.umd.cs.findbugs.ba;

import java.util.*;

/**
 * Factory for ValueNumbers.
 * A single Factory must be used to create all of the ValueNumbers
 * for a method.
 *
 * @author David Hovemeyer
 * @see ValueNumber
 */
public class ValueNumberFactory {
	/**
	 * Store all allocated value numbers.
	 */
	private ArrayList<ValueNumber> allocatedValueList = new ArrayList<ValueNumber>();

	/**
	 * Create a fresh (unique) value number.
	 */
	public ValueNumber createFreshValue() {
		ValueNumber result = new ValueNumber(getNumValuesAllocated());
		allocatedValueList.add(result);
		return result;
	}

	/**
	 * Return a previously allocated value.
	 */
	public ValueNumber forNumber(int number) {
		if (number >= getNumValuesAllocated())
			throw new IllegalArgumentException("Value " + number + " has not been allocated");
		return allocatedValueList.get(number);
	}

	/**
	 * Get the number of values which have been created.
	 */
	public int getNumValuesAllocated() {
		return allocatedValueList.size();
	}

	/**
	 * Compact the value numbers produced by this factory.
	 *
	 * @param map                array mapping old numbers to new numbers
	 * @param numValuesAllocated the number of values allocated in the new numbering
	 */
	public void compact(int[] map, int numValuesAllocated) {
		ArrayList<ValueNumber> oldList = this.allocatedValueList;
		ArrayList<ValueNumber> newList = new ArrayList<ValueNumber>(Collections.nCopies(numValuesAllocated, (ValueNumber) null));

		for (Iterator<ValueNumber> i = oldList.iterator(); i.hasNext();) {
			ValueNumber value = i.next();
			int newNumber = map[value.getNumber()];
			if (newNumber >= 0) {
				// Note: because we are simply assigning new numbers to the
				// old ValueNumber objects, their flags remain valid.
				value.number = newNumber;
				newList.set(newNumber, value);
			}
		}

		this.allocatedValueList = newList;
	}

}

// vim:ts=4