001 /* WildcardType.java -- A wildcard type expression e.g. ? extends String
002 Copyright (C) 2004, 2005 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
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009 any later version.
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020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
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027 permission to link this library with independent modules to produce an
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036 exception statement from your version. */
037
038
039 package java.lang.reflect;
040
041 /**
042 * Represents a wildcard type expression, where the type variable
043 * is unnamed. The simplest example of this is <code>?</code>,
044 * which represents any unbounded type. Another example is
045 * <code>? extends Number</code>, which specifies any type
046 * which is a subclass of <code>Number</code> (<code>Number</code>
047 * is the upper bound).
048 * </p>
049 * <p>
050 * <code>? super String</code> gives the type a less common lower bound,
051 * which means that the type must be either a <code>String</code> or one
052 * of its superclasses. This can be useful in working with collections.
053 * You may want a method to add instances of a class to a collection
054 * with a more generic type (e.g. adding <code>String</code>s to
055 * a list of <code>Object</code>s), but don't want to allow users
056 * to pass in a collection with a more specific type.
057 * </p>
058 *
059 * @author Tom Tromey (tromey@redhat.com)
060 * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
061 * @since 1.5
062 */
063 public interface WildcardType extends Type
064 {
065
066 /**
067 * <p>
068 * Returns an array of <code>Type</code>s, which specify the
069 * lower bounds of this type. The default lower bound is
070 * <code>null</code>, which causes this method to return an
071 * empty array.
072 * </p>
073 * <p>
074 * In generating the array of <code>Type</code>s, each
075 * <code>ParameterizedType</code> or <code>TypeVariable</code> is
076 * created, (see the documentation for these classes for details of this
077 * process), if necessary, while all other types are simply
078 * resolved.
079 * </p>
080 *
081 * @return an array of <code>Type</code> objects, representing
082 * the wildcard type's lower bounds.
083 * @throws TypeNotPresentException if any of the types referred to by
084 * the lower bounds of this type do not actually exist.
085 * @throws MalformedParameterizedTypeException if any of the types
086 * refer to a type which can not be instantiated.
087 */
088 Type[] getLowerBounds();
089
090 /**
091 * <p>
092 * Returns an array of <code>Type</code>s, which specify the
093 * upper bounds of this type. The default upper bound is
094 * <code>Object</code>, which causes this method to return an
095 * array, containing just the <code>Type</code> instance for
096 * <code>Object</code>.
097 * </p>
098 * <p>
099 * In generating the array of <code>Type</code>s, each
100 * <code>ParameterizedType</code> or <code>TypeVariable</code> is
101 * created, (see the documentation for these classes for details of this
102 * process), if necessary, while all other types are simply
103 * resolved.
104 * </p>
105 *
106 * @return an array of <code>Type</code> objects, representing
107 * the wildcard type's upper bounds.
108 * @throws TypeNotPresentException if any of the types referred to by
109 * the upper bounds of this type do not actually exist.
110 * @throws MalformedParameterizedTypeException if any of the types
111 * refer to a type which can not be instantiated.
112 */
113 Type[] getUpperBounds();
114
115 }