1   /*
    2    * Copyright (c) 2005, 2006, Oracle and/or its affiliates. All rights reserved.
    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    4    *
    5    * This code is free software; you can redistribute it and/or modify it
    6    * under the terms of the GNU General Public License version 2 only, as
    7    * published by the Free Software Foundation.  Oracle designates this
    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
   10    *
   11    * This code is distributed in the hope that it will be useful, but WITHOUT
   12    * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   14    * version 2 for more details (a copy is included in the LICENSE file that
   15    * accompanied this code).
   16    *
   17    * You should have received a copy of the GNU General Public License version
   18    * 2 along with this work; if not, write to the Free Software Foundation,
   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
   21    * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   22    * or visit www.oracle.com if you need additional information or have any
   23    * questions.
   24    */
   25   
   26   package javax.lang.model.type;
   27   
   28   import javax.lang.model.element;
   29   import javax.lang.model.util.Types;
   30   
   31   /**
   32    * Represents a type in the Java programming language.
   33    * Types include primitive types, declared types (class and interface types),
   34    * array types, type variables, and the null type.
   35    * Also represented are wildcard type arguments,
   36    * the signature and return types of executables,
   37    * and pseudo-types corresponding to packages and to the keyword {@code void}.
   38    *
   39    * <p> Types should be compared using the utility methods in {@link
   40    * Types}.  There is no guarantee that any particular type will always
   41    * be represented by the same object.
   42    *
   43    * <p> To implement operations based on the class of an {@code
   44    * TypeMirror} object, either use a {@linkplain TypeVisitor visitor}
   45    * or use the result of the {@link #getKind} method.  Using {@code
   46    * instanceof} is <em>not</em> necessarily a reliable idiom for
   47    * determining the effective class of an object in this modeling
   48    * hierarchy since an implementation may choose to have a single
   49    * object implement multiple {@code TypeMirror} subinterfaces.
   50    *
   51    * @author Joseph D. Darcy
   52    * @author Scott Seligman
   53    * @author Peter von der Ah&eacute;
   54    * @see Element
   55    * @see Types
   56    * @since 1.6
   57    */
   58   public interface TypeMirror {
   59   
   60       /**
   61        * Returns the {@code kind} of this type.
   62        *
   63        * @return the kind of this type
   64        */
   65       TypeKind getKind();
   66   
   67       /**
   68        * Obeys the general contract of {@link Object#equals Object.equals}.
   69        * This method does not, however, indicate whether two types represent
   70        * the same type.
   71        * Semantic comparisons of type equality should instead use
   72        * {@link Types#isSameType(TypeMirror, TypeMirror)}.
   73        * The results of {@code t1.equals(t2)} and
   74        * {@code Types.isSameType(t1, t2)} may differ.
   75        *
   76        * @param obj  the object to be compared with this type
   77        * @return {@code true} if the specified object is equal to this one
   78        */
   79       boolean equals(Object obj);
   80   
   81       /**
   82        * Obeys the general contract of {@link Object#hashCode Object.hashCode}.
   83        *
   84        * @see #equals
   85        */
   86       int hashCode();
   87   
   88       /**
   89        * Returns an informative string representation of this type.  If
   90        * possible, the string should be of a form suitable for
   91        * representing this type in source code.  Any names embedded in
   92        * the result are qualified if possible.
   93        *
   94        * @return a string representation of this type
   95        */
   96       String toString();
   97   
   98       /**
   99        * Applies a visitor to this type.
  100        *
  101        * @param <R> the return type of the visitor's methods
  102        * @param <P> the type of the additional parameter to the visitor's methods
  103        * @param v   the visitor operating on this type
  104        * @param p   additional parameter to the visitor
  105        * @return a visitor-specified result
  106        */
  107       <R, P> R accept(TypeVisitor<R, P> v, P p);
  108   }