abstractpredicate.java

一个关于java 的常用工具包

package org.jutil.predicate;

import java.util.Iterator;
import java.util.Collection;
import java.util.Arrays;
import java.util.List;
import java.util.ConcurrentModificationException;
import org.jutil.java.collections.CollectionOperator;

/**
 * @path    $Source: /cvsroot/org-jutil/jutil.org/src/org/jutil/predicate/AbstractPredicate.java,v $
 * @version $Revision: 1.2 $
 * @date    $Date: 2002/09/07 09:24:11 $
 * @state   $State: Exp $
 * @author  ?????
 * @release $Name:  $
 */
public abstract class AbstractPredicate implements Predicate {
  
   /**
    * See superclass
    */
   public /*@ pure @*/ boolean exists(Collection collection) throws ConcurrentModificationException, Exception {
    boolean acc = false;
    if (collection != null) {
      Iterator iter = collection.iterator();
      // variant : the number of elements in the explicit collection that
      //           have not yet been checked.
      // invariant : acc == false if none of the previous elements in the
      //             explicit collection satisfies the criterion.
      //             Otherwise, it is true.
      while (iter.hasNext() && (!acc)) {
        acc = eval(iter.next());
      }
    }
    return acc;
  }
 
   /**
    * See superclass
    */
  public /*@ pure @*/ boolean forall(Collection collection) throws ConcurrentModificationException, Exception {
    boolean acc = true;
    if(collection != null) {
      Iterator iter = collection.iterator();
      // variant : the number of elements in the explicit collection that
      //           have not yet been checked.
      // invariant : acc == true if all previous elements in the explicit collection
      //             satisfy the criterion. Otherwise, it is false.
      while (iter.hasNext() && acc) {
        acc = eval(iter.next());
      }
    }
    return acc;
  }

   /**
    * See superclass
    */
  public /*@ pure @*/ int count(Collection collection) throws ConcurrentModificationException, Exception {
		int count = 0;
		if (collection != null) {
			Iterator iter = collection.iterator();
			while (iter.hasNext()) {
				if (eval(iter.next())) {
					count++;
				}
			}
		}
		return count;
  }

   /**
    * See superclass
    */
  public void filter(Collection collection) throws ConcurrentModificationException, Exception {
   	if (collection != null) {
			// Make a backup, just in case something goes wrong
			Object[] backup = collection.toArray();
			try {
   	    Iterator iter = collection.iterator();
   	    while (iter.hasNext()) {
   	      if (! eval(iter.next())) {
   	        iter.remove();
   	      }
   	    }
   	  }
			catch(Exception exc) {
				// clear whatever is left in the collection
				collection.clear();
				collection.addAll(Arrays.asList(backup));
				throw exc;
			}
		}
  }

  /**
   * See superclass
   */
	public final boolean equals(Object other) {
		//default implementation
		return (other == this);
	}

  /**
   * See superclass
   */
	public int nbSubPredicates() {
		return getSubPredicates().size();
	}
}
/*
 * <copyright>Copyright (C) 1997-2002. This software is copyrighted by 
 * the people and entities mentioned after the "@author" tags above, on 
 * behalf of the JUTIL.ORG Project. The copyright is dated by the dates 
 * after the "@date" tags above. All rights reserved.
 * This software is published under the terms of the JUTIL.ORG Software
 * License version 1.1 or later, a copy of which has been included with
 * this distribution in the LICENSE file, which can also be found at
 * http://org-jutil.sourceforge.net/LICENSE. This software is distributed 
 * WITHOUT ANY WARRANTY; without even the implied warranty of 
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 
 * See the JUTIL.ORG Software License for more details. For more information,
 * please see http://org-jutil.sourceforge.net/</copyright>
 */