referencetype.java

Java Bytecode Editor 是一个 JAVA 的字节码反汇编和修改器。它可以很方便的修改已经编译成 Class 文件的 JAVA 文件。

package org.apache.bcel.generic;

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 *       "This product includes software developed by the
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import org.apache.bcel.Constants;
import org.apache.bcel.Repository;
import org.apache.bcel.classfile.JavaClass;

/**
 * Super class for object and array types.
 *
 * @version $Id: ReferenceType.java,v 1.1 2005/12/16 14:11:25 andos Exp $
 * @author  <A HREF="mailto:[e-mail]">M. Dahm</A>
 */
public abstract 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 (