typefilter.java

一个关于java 的常用工具包

package org.jutil.java.collections;


/**
 * <p>A class of filters that use the type of an object as criterion.</p>
 *
 * <center>
 *  <img src="doc-files/TypeFilter.png"/>
 * </center>
 *
 * <p>This filter uses the type of elements of the filtered collection as criterium.
 * The type to use in the criterium is given as an argument during construction.
 * Subclasses exist how to deal with the type.</p>
 *
 * <p>The type can be passed to the <code>TypeFilter</code> with a <code>Class</code> object, or with a
 * <code>String</code> that equals its name. The latter is necessary when defining <code>Filter</code>
 * constants in an interface.</p>
 *
 * <p>For using a <code>TypeFilter</code>, no class has to be created. Just create a new <code>TypeFilter</code>
 * with the requested type as an argument.</p>
 *
 * <pre><code>
 * new TypeFilter(myPackage.MyClass.class).retain(collection);
 * </code></pre>
 * <pre><code>
 * new TypeFilter("myPackage.MyClass").discard(collection);
 * </code></pre>
 *
 * @path    $Source: /cvsroot/org-jutil/jutil.org/src/org/jutil/java/collections/TypeFilter.java,v $
 * @version $Revision: 1.11 $
 * @date    $Date: 2002/07/21 17:56:59 $
 * @state   $State: Exp $
 * @author  Jan Dockx
 * @author  Marko van Dooren
 * @release $Name:  $
 */
public class TypeFilter extends Filter {
  
	/* The revision of this class */
	public final static String CVS_REVISION ="$Revision: 1.11 $";

  /**
   * <p>A new Type Filter that filters objects based on type <type> from the
   * filtered collections.</p>
   *
   * @param type
   *        The type to be filtered.
   */
 /*@
	 @ public behavior
	 @
   @ // The given type may not be null.
   @ pre type != null;
   @
   @ // The type of this TypeFilter is set to the given type.
   @ post getType() == type;
   @*/
  public TypeFilter(Class type) {
    $type = type;
  }
  
  /**
   * <p>A new Type Filter that filters objects based on the type with the
   * given name from the filtered collections.</p>
   *
   * @param name
   *        The name of the type to be filtered.
   */
 /*@
	 @ public behavior
	 @
   @ // <name> may not be null
   @ pre name != null;
   @ // <name> must be a valid classname
   @ 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 TypeFilter(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 TypeFilter.
	 */
 /*@
	 @ public behavior
	 @
	 @ post \result != null;
	 @*/
  public final Class getType() {
    return $type;
  }
  
	/**
	 * The type to be used in the filter.
	 */
 /*@
   @ private invariant $type != null;
   @*/
  private Class $type;

	/**
	 * See superclass
	 */
 /*@
	 @ also public behavior
	 @
   @ // <element> is of the desired type.
   @ post \result == getType().isInstance(element);
   @*/
  public final boolean criterion(Object element) {
    return getType().isInstance(element);
  }

}

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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.
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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
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