typepredicate.java

一个关于java 的常用工具包

package org.jutil.predicate;

/**
 * <p>A class of predicate that check whether or not an object conforms to
 * a certain type.</p>
 *
 * <center><img src="doc-files/TypePredicate.png"/></center>
 *
 * <p>This class is typically used as follows:</p>
 * <pre><code>
 * TotalPredicate predicate = new TypePredicate(MyClass.class);
 * </code></pre>
 *
 * <p>When a <code>TypePredicate</code> is used as a constant in an interface,
 * the <code>.class</code> operator will return <code>null</code>, so in that 
 * case you must pass the name of the class as a <code>String</code>:</p>
 * <pre><code>
 * TotalPredicate predicate = new TypePredicate("mypackage.MyClass");
 * </code></pre>
 *
 * @path    $Source: /cvsroot/org-jutil/jutil.org/src/org/jutil/predicate/TypePredicate.java,v $
 * @version $Revision: 1.3 $
 * @date    $Date: 2002/07/21 16:06:38 $
 * @state   $State: Exp $
 * @author  Marko van Dooren
 * @author  Jan Dockx
 * @release $Name:  $
 */
public class TypePredicate extends PrimitiveTotalPredicate {

	/* The revision of this class */
	public final static String CVS_REVISION ="$Revision: 1.3 $";

  /**
   * <p>Initialize a new TypePredicate that check whether or not objects
	 * are from a give type.</p>
   *
   * @param type
   *        The type.
   */
 /*@
	 @ public behavior
	 @
   @ pre type != null;
   @
   @ post getType() == type;
   @*/
  public TypePredicate(Class type) {
    $type = type;
  }

  /**
   * <p>Initialize a new TypePredicate based on the type with the given name.</p>
   *
   * @param name
   *        The name of the type.
   */
 /*@
	 @ public behavior
	 @
   @ pre name != null;
   @ pre (* <name> must be a valid classname *);
   @
   @ // The type of this TypeFilter is set to the type
   @ // with the given name.
   @ post getType() == Class.forName(name);
	 @
	 @ signals (LinkageError) (* something went wrong *);
	 @ signals (ExceptionInInitializerError) (* something went wrong *);
	 @ signals (IllegalArgumentException) (* Illegal Class Name *);
   @*/
  public TypePredicate(String name) throws LinkageError,ExceptionInInitializerError, IllegalArgumentException {
    try {
      $type = Class.forName(name);
    }
    catch(ClassNotFoundException exc) {
      throw new IllegalArgumentException("Illegal class name : "+name);
    }
  }

	/**
	 * Return the type of this TypePredicate.
	 */
 /*@
	 @ public behavior
	 @
	 @ post \result != null;
	 @*/
  public Class getType() {
    return $type;
  }

 /*@
	 @ also public behavior
	 @
	 @ post \result == getType().isInstance(object);
	 @*/
	public boolean eval(Object object) {
		return getType().isInstance(object);
	}

	/**
	 * The type to be used in the filter.
	 */
 /*@
   @ private invariant $type != null;
   @*/
  private Class $type;
	
}
/*
 * <copyright>Copyright (C) 1997-2001. 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>
 */