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From scolebou...@apache.org
Subject cvs commit: jakarta-commons-sandbox/pattern/src/java/org/apache/commons/pattern/immutable ImmutableUtils.java Immutable.java
Date Sat, 29 Jun 2002 18:39:32 GMT
scolebourne    2002/06/29 11:39:32

  Added:       pattern/src/java/org/apache/commons/pattern/immutable
                        ImmutableUtils.java Immutable.java
  Log:
  Initial checkin
  
  Revision  Changes    Path
  1.1                  jakarta-commons-sandbox/pattern/src/java/org/apache/commons/pattern/immutable/ImmutableUtils.java
  
  Index: ImmutableUtils.java
  ===================================================================
  /* ====================================================================
   * The Apache Software License, Version 1.1
   *
   * Copyright (c) 2002 The Apache Software Foundation.  All rights
   * reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   *
   * 3. The end-user documentation included with the redistribution, if
   *    any, must include the following acknowlegement:
   *       "This product includes software developed by the
   *        Apache Software Foundation (http://www.apache.org/)."
   *    Alternately, this acknowlegement may appear in the software itself,
   *    if and wherever such third-party acknowlegements normally appear.
   *
   * 4. The names "The Jakarta Project", "Commons", and "Apache Software
   *    Foundation" must not be used to endorse or promote products derived
   *    from this software without prior written permission. For written
   *    permission, please contact apache@apache.org.
   *
   * 5. Products derived from this software may not be called "Apache"
   *    nor may "Apache" appear in their names without prior written
   *    permission of the Apache Software Foundation.
   *
   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   */
  package org.apache.commons.pattern.immutable;
  
  import java.util.Collections;
  import java.util.HashSet;
  import java.util.Locale;
  import java.util.Set;
  /**
   * <code>ImmutableUtils</code> provides utilities for the Immutable pattern
   * interface.
   *
   * @author <a href="mailto:scolebourne@joda.org">Stephen Colebourne</a>
   * @version $Id: ImmutableUtils.java,v 1.1 2002/06/29 18:39:32 scolebourne Exp $
   */
  public class ImmutableUtils {
  
      /**
       * JVM shared Set of immutable classes
       */
      public static Set cImmutableClasses = new HashSet();
      
      static {
          addImmutableClass(String.class);
          addImmutableClass(Boolean.class);
          addImmutableClass(Byte.class);
          addImmutableClass(Character.class);
          addImmutableClass(Short.class);
          addImmutableClass(Integer.class);
          addImmutableClass(Long.class);
          addImmutableClass(Float.class);
          addImmutableClass(Double.class);
          addImmutableClass(Class.class);
          addImmutableClass(Locale.class);
          try {
              addImmutableClass(Class.forName("java.util.Currency"));
          } catch (ClassNotFoundException ex) {
              // ignore
          }
          try {
              addImmutableClass(Class.forName("java.net.URI"));
          } catch (ClassNotFoundException ex) {
              // ignore
          }
          // The following have been rejected:
          // Method, Field, Constructor (mutable with setAccessible method)
          // BigDecimal, BigInteger (not final)
      }
  
      /**
       * Restructive constructor
       */
      private ImmutableUtils() {
          super();
      }
  
      /**
       * Add a class to the list of known Immutable classes. This method 
       * is shared across the JVM, thus should usually only be called 
       * during initialisation.
       * <p>
       * This method is used to indicate that a class which does not 
       * implement Immutable is in fact immutable.
       * 
       * @param the class to be added to the Set of immutable classes, null ignored
       */
      public static void addImmutableClass(Class cls) {
          if (cls != null) {
              cImmutableClasses.add(cls);
          }
      }
  
      /**
       * Get the Set of Class objects representing those classes that
       * are immutable but don't implement the interface.
       * 
       * @return the Set of immutable classes
       */
      public static Set getImmutableClasses() {
          return Collections.unmodifiableSet(cImmutableClasses);
      }
  
      /**
       * Tests if the object is immutable. This checks if it implements
       * the Immutable interface, or if it is a known immutable type.
       * 
       * @param object  the object to check
       * @throws IllegalArgumentException if the object specified is null
       */
      public static boolean isImmutable(Object object) {
          if (object == null) {
              throw new IllegalArgumentException("The object must not be null");
          }
          if (object instanceof Immutable) {
              return true;
          }
          return isImmutable(object.getClass());
      }
  
      /**
       * Tests if the object is immutable. This checks if it implements
       * the Immutable interface, or if it is a known immutable type.
       * 
       * @param cls  the class to check
       * @throws IllegalArgumentException if the class specified is null
       */
      public static boolean isImmutable(Class cls) {
          if (cls == null) {
              throw new IllegalArgumentException("The class must not be null");
          }
          if (Immutable.class.isAssignableFrom(cls)) {
              return true;
          }
          return cImmutableClasses.contains(cls);
      }
  
  }
  
  
  
  1.1                  jakarta-commons-sandbox/pattern/src/java/org/apache/commons/pattern/immutable/Immutable.java
  
  Index: Immutable.java
  ===================================================================
  /* ====================================================================
   * The Apache Software License, Version 1.1
   *
   * Copyright (c) 2002 The Apache Software Foundation.  All rights
   * reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   *
   * 3. The end-user documentation included with the redistribution, if
   *    any, must include the following acknowlegement:
   *       "This product includes software developed by the
   *        Apache Software Foundation (http://www.apache.org/)."
   *    Alternately, this acknowlegement may appear in the software itself,
   *    if and wherever such third-party acknowlegements normally appear.
   *
   * 4. The names "The Jakarta Project", "Commons", and "Apache Software
   *    Foundation" must not be used to endorse or promote products derived
   *    from this software without prior written permission. For written
   *    permission, please contact apache@apache.org.
   *
   * 5. Products derived from this software may not be called "Apache"
   *    nor may "Apache" appear in their names without prior written
   *    permission of the Apache Software Foundation.
   *
   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   */
  package org.apache.commons.pattern.immutable;
  
  /**
   * <code>Immutable</code> defines an interface implemented by classes that
   * are immutable. To comply:
   * <ul>
   * <li>The class must be final
   * <li>All fields must be private
   * <li>The class must have no set methods, or other methods that modify
   *  the object
   * <li>If the class holds a mutable object, that object must be cloned in 
   *  the constructor, any get method and during deserialization using a
   *  readResolve() method
   * <li>The class should have a readResolve method
   * </ul>
   * It should be noted that not every immutable class that you write will
   * necessarily implement Immutable. Immutable is reserved for data classes,
   * similar to String and Integer. The toString() method definition must
   * be read carefully in particular.
   * 
   * @author <a href="mailto:scolebourne@joda.org">Stephen Colebourne</a>
   * @version $Id: Immutable.java,v 1.1 2002/06/29 18:39:32 scolebourne Exp $
   */
  public interface Immutable {
      
      /**
       * Compare this object to another. Immutable objects are often used
       * in Maps, so the equals() method should be designed with care.
       *
       * @see java.lang.Object#equals()
       * @return true if this object equals the passed in object
       */
      public boolean equals(Object object);
      
      /**
       * Get a hash code that complies with the normal rules laid out in
       * <code>java.lang.Object</code>. Immutable objects are often used
       * in Maps, so the hashCode() method should be designed with care.
       *
       * @see java.lang.Object#hashCode()
       * @return an integer hashcode for the object
       */
      public int hashCode();
      
      /**
       * Return the entire information about the identifier as a String.
       * <p>
       * The method may not return null. The format of the String should
       * be such that it can be parsed back to recreate the object. Normally,
       * the class will have a static <code>parse(String)</code> method for
       * this purpose.
       * <p>
       * This method is not a debugging method, and thus StringBuffer
       * should be used to append Strings, not the + operator for
       * performance reasons.
       *
       * @return a string representing the entire state of the immutable object
       */
      public String toString();
      
  }
  
  
  

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