referencetype.java

该开源工具主要用于class文件的操作

package org.apache.bcel.generic;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 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 acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache BCEL" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact [e-mail].
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache BCEL", nor may "Apache" appear in their name, 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/>.
 */
import org.apache.bcel.Constants;
import org.apache.bcel.Repository;
import org.apache.bcel.classfile.JavaClass;

/** 
 * Super class for objects and arrays.
 *
 * @version $Id: ReferenceType.java,v 1.1.1.1 2001/10/29 20:00:26 jvanzyl Exp $
 * @author  <A HREF="mailto:[e-mail]">M. Dahm</A>
 */
public class ReferenceType extends Type {
  protected ReferenceType(byte t, String s) {
    super(t, s);
  }

  /** Class is non-abstract but not instantiable from the outside
   */
  ReferenceType() {
    super(Constants.T_OBJECT, "<null object>");
  }

  /**
   * Return true iff this type is castable to another type t as defined in
   * the JVM specification.  The case where this is Type.NULL is not
   * defined (see the CHECKCAST definition in the JVM specification).
   * However, because e.g. CHECKCAST doesn't throw a
   * ClassCastException when casting a null reference to any Object,
   * true is returned in this case.
   */
  public boolean isCastableTo(Type t){
    if(this.equals(Type.NULL))
      return true;		// If this is ever changed in isAssignmentCompatible()

    return isAssignmentCompatibleWith(t); /* Yes, it's true: It's the same definition.
					   * See vmspec2 AASTORE / CHECKCAST definitions.
					   */
  }

  /**
   * Return true iff this is assignment compatible with another type t
   * as defined in the JVM specification; see the AASTORE definition
   * there.
   */
  public boolean isAssignmentCompatibleWith(Type t) {
    if(!(t instanceof ReferenceType))
      return false;

    ReferenceType T = (ReferenceType)t;

    if(this.equals(Type.NULL))
      return true; // This is not explicitely stated, but clear. Isn't it?

    /* If this is a class type then
     */
    if((this instanceof ObjectType) && (((ObjectType) this).referencesClass())) {
      /* If T is a class type, then this must be the same class as T,
         or this must be a subclass of T;
      */
      if((T instanceof ObjectType) && (((ObjectType) T).referencesClass())) {
	if(this.equals(T))
	  return true;

	if(Repository.instanceOf( ((ObjectType) this).getClassName(),
				  ((ObjectType) T).getClassName()))
	  return true;
      }

      /* If T is an interface type, this must implement interface T.
       */
      if ((T instanceof ObjectType) && (((ObjectType) T).referencesInterface())) {
	if (Repository.implementationOf( ((ObjectType) this).getClassName(),
					 ((ObjectType) T).getClassName() ))
	  return true;
      }
    }

    /* If this is an interface type, then:
     */
    if ((this instanceof ObjectType) && (((ObjectType) this).referencesInterface())){
      /* If T is a class type, then T must be Object (