1 /*
2 * Copyright (c) 2018, 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 package java.lang.constant;
26
27 import java.lang.invoke.TypeDescriptor;
28 import java.util.stream.Stream;
29
30 import sun.invoke.util.Wrapper;
31
32 import static java.lang.constant.ConstantUtils.binaryToInternal;
33 import static java.lang.constant.ConstantUtils.dropLastChar;
34 import static java.lang.constant.ConstantUtils.internalToBinary;
35 import static java.lang.constant.ConstantUtils.validateMemberName;
36 import static java.util.Objects.requireNonNull;
37 import static java.util.stream.Collectors.joining;
38
39 /**
40 * A <a href="package-summary.html#nominal">nominal descriptor</a> for a
41 * {@link Class} constant.
42 *
43 * <p>For common system types, including all the primitive types, there are
44 * predefined {@linkplain ClassDesc} constants in {@link ConstantDescs}.
45 * (The {@code java.lang.constant} APIs consider {@code void} to be a primitive type.)
46 * To create a {@linkplain ClassDesc} for a class or interface type, use {@link #of} or
47 * {@link #ofDescriptor(String)}; to create a {@linkplain ClassDesc} for an array
48 * type, use {@link #ofDescriptor(String)}, or first obtain a
49 * {@linkplain ClassDesc} for the component type and then call the {@link #arrayType()}
50 * or {@link #arrayType(int)} methods.
51 *
52 * @apiNote In the future, if the Java language permits, {@linkplain ClassDesc}
53 * may become a {@code sealed} interface, which would prohibit subclassing except
54 * by explicitly permitted types. Non-platform classes should not implement
55 * {@linkplain ClassDesc} directly.
56 *
57 * @see ConstantDescs
58 *
59 * @since 12
60 */
61 public interface ClassDesc
62 extends ConstantDesc,
63 TypeDescriptor.OfField<ClassDesc> {
64
65 /**
66 * Returns a {@linkplain ClassDesc} for a class or interface type,
67 * given the name of the class or interface, such as {@code "java.lang.String"}.
68 * (To create a descriptor for an array type, either use {@link #ofDescriptor(String)}
69 * or {@link #arrayType()}; to create a descriptor for a primitive type, use
70 * {@link #ofDescriptor(String)} or use the predefined constants in
71 * {@link ConstantDescs}).
72 *
73 * @param name the fully qualified (dot-separated) binary class name
74 * @return a {@linkplain ClassDesc} describing the desired class
75 * @throws NullPointerException if any argument is {@code null}
76 * @throws IllegalArgumentException if the name string is not in the
77 * correct format
78 */
79 static ClassDesc of(String name) {
80 ConstantUtils.validateBinaryClassName(requireNonNull(name));
81 return ClassDesc.ofDescriptor("L" + binaryToInternal(name) + ";");
82 }
83
84 /**
85 * Returns a {@linkplain ClassDesc} for a class or interface type,
86 * given a package name and the unqualified (simple) name for the
87 * class or interface.
88 *
89 * @param packageName the package name (dot-separated); if the package
90 * name is the empty string, the class is considered to
91 * be in the unnamed package
92 * @param className the unqualified (simple) class name
93 * @return a {@linkplain ClassDesc} describing the desired class
94 * @throws NullPointerException if any argument is {@code null}
95 * @throws IllegalArgumentException if the package name or class name are
96 * not in the correct format
97 */
98 static ClassDesc of(String packageName, String className) {
99 ConstantUtils.validateBinaryClassName(requireNonNull(packageName));
100 validateMemberName(requireNonNull(className));
101 return ofDescriptor(String.format("L%s%s%s;",
102 binaryToInternal(packageName),
103 (packageName.length() > 0 ? "/" : ""),
104 className));
105 }
106
107 /**
108 * Returns a {@linkplain ClassDesc} given a descriptor string for a class,
109 * interface, array, or primitive type.
110 *
111 * @apiNote
112 *
113 * A field type descriptor string for a non-array type is either
114 * a one-letter code corresponding to a primitive type
115 * ({@code "J", "I", "C", "S", "B", "D", "F", "Z", "V"}), or the letter {@code "L"}, followed
116 * by the fully qualified binary name of a class, followed by {@code ";"}.
117 * A field type descriptor for an array type is the character {@code "["}
118 * followed by the field descriptor for the component type. Examples of
119 * valid type descriptor strings include {@code "Ljava/lang/String;"}, {@code "I"},
120 * {@code "[I"}, {@code "V"}, {@code "[Ljava/lang/String;"}, etc.
121 * See JVMS 4.3.2 ("Field Descriptors") for more detail.
122 *
123 * @param descriptor a field descriptor string
124 * @return a {@linkplain ClassDesc} describing the desired class
125 * @throws NullPointerException if any argument is {@code null}
126 * @throws IllegalArgumentException if the name string is not in the
127 * correct format
128 * @jvms 4.3.2 Field Descriptors
129 */
130 static ClassDesc ofDescriptor(String descriptor) {
131 requireNonNull(descriptor);
132 return (descriptor.length() == 1)
133 ? new PrimitiveClassDescImpl(descriptor)
134 : new ReferenceClassDescImpl(descriptor);
135 }
136
137 /**
138 * Returns a {@linkplain ClassDesc} for an array type whose component type
139 * is described by this {@linkplain ClassDesc}.
140 *
141 * @return a {@linkplain ClassDesc} describing the array type
142 */
143 default ClassDesc arrayType() {
144 return arrayType(1);
145 }
146
147 /**
148 * Returns a {@linkplain ClassDesc} for an array type of the specified rank,
149 * whose component type is described by this {@linkplain ClassDesc}.
150 *
151 * @param rank the rank of the array
152 * @return a {@linkplain ClassDesc} describing the array type
153 * @throws IllegalArgumentException if the rank is zero or negative
154 */
155 default ClassDesc arrayType(int rank) {
156 if (rank <= 0)
157 throw new IllegalArgumentException("rank: " + rank);
158 return ClassDesc.ofDescriptor("[".repeat(rank) + descriptorString());
159 }
160
161 /**
162 * Returns a {@linkplain ClassDesc} for a nested class of the class or
163 * interface type described by this {@linkplain ClassDesc}.
164 *
165 * @apiNote
166 *
167 * Example: If descriptor {@code d} describes the class {@code java.util.Map}, a
168 * descriptor for the class {@code java.util.Map.Entry} could be obtained
169 * by {@code d.nested("Entry")}.
170 *
171 * @param nestedName the unqualified name of the nested class
172 * @return a {@linkplain ClassDesc} describing the nested class
173 * @throws NullPointerException if any argument is {@code null}
174 * @throws IllegalStateException if this {@linkplain ClassDesc} does not
175 * describe a class or interface type
176 * @throws IllegalArgumentException if the nested class name is invalid
177 */
178 default ClassDesc nested(String nestedName) {
179 validateMemberName(nestedName);
180 if (!isClassOrInterface())
181 throw new IllegalStateException("Outer class is not a class or interface type");
182 return ClassDesc.ofDescriptor(String.format("%s$%s;", dropLastChar(descriptorString()), nestedName));
183 }
184
185 /**
186 * Returns a {@linkplain ClassDesc} for a nested class of the class or
187 * interface type described by this {@linkplain ClassDesc}.
188 *
189 * @param firstNestedName the unqualified name of the first level of nested class
190 * @param moreNestedNames the unqualified name(s) of the remaining levels of
191 * nested class
192 * @return a {@linkplain ClassDesc} describing the nested class
193 * @throws NullPointerException if any argument is {@code null}
194 * @throws IllegalStateException if this {@linkplain ClassDesc} does not
195 * describe a class or interface type
196 * @throws IllegalArgumentException if the nested class name is invalid
197 */
198 default ClassDesc nested(String firstNestedName, String... moreNestedNames) {
199 if (!isClassOrInterface())
200 throw new IllegalStateException("Outer class is not a class or interface type");
201 return moreNestedNames.length == 0
202 ? nested(firstNestedName)
203 : nested(firstNestedName + Stream.of(moreNestedNames).collect(joining("$", "$", "")));
204 }
205
206 /**
207 * Returns whether this {@linkplain ClassDesc} describes an array type.
208 *
209 * @return whether this {@linkplain ClassDesc} describes an array type
210 */
211 default boolean isArray() {
212 return descriptorString().startsWith("[");
213 }
214
215 /**
216 * Returns whether this {@linkplain ClassDesc} describes a primitive type.
217 *
218 * @return whether this {@linkplain ClassDesc} describes a primitive type
219 */
220 default boolean isPrimitive() {
221 return descriptorString().length() == 1;
222 }
223
224 /**
225 * Returns whether this {@linkplain ClassDesc} describes a class or interface type.
226 *
227 * @return whether this {@linkplain ClassDesc} describes a class or interface type
228 */
229 default boolean isClassOrInterface() {
230 return descriptorString().startsWith("L");
231 }
232
233 /**
234 * Returns the component type of this {@linkplain ClassDesc}, if it describes
235 * an array type, or {@code null} otherwise.
236 *
237 * @return a {@linkplain ClassDesc} describing the component type, or {@code null}
238 * if this descriptor does not describe an array type
239 */
240 default ClassDesc componentType() {
241 return isArray() ? ClassDesc.ofDescriptor(descriptorString().substring(1)) : null;
242 }
243
244 /**
245 * Returns the package name of this {@linkplain ClassDesc}, if it describes
246 * a class or interface type.
247 *
248 * @return the package name, or the empty string if the class is in the
249 * default package, or this {@linkplain ClassDesc} does not describe a class or interface type
250 */
251 default String packageName() {
252 if (!isClassOrInterface())
253 return "";
254 String className = internalToBinary(ConstantUtils.dropFirstAndLastChar(descriptorString()));
255 int index = className.lastIndexOf('.');
256 return (index == -1) ? "" : className.substring(0, index);
257 }
258
259 /**
260 * Returns a human-readable name for the type described by this descriptor.
261 *
262 * @implSpec
263 * <p>The default implementation returns the simple name
264 * (e.g., {@code int}) for primitive types, the unqualified class name
265 * for class or interface types, or the display name of the component type
266 * suffixed with the appropriate number of {@code []} pairs for array types.
267 *
268 * @return the human-readable name
269 */
270 default String displayName() {
271 if (isPrimitive())
272 return Wrapper.forBasicType(descriptorString().charAt(0)).primitiveSimpleName();
273 else if (isClassOrInterface()) {
274 return descriptorString().substring(Math.max(1, descriptorString().lastIndexOf('/') + 1),
275 descriptorString().length() - 1);
276 }
277 else if (isArray()) {
278 int depth = ConstantUtils.arrayDepth(descriptorString());
279 ClassDesc c = this;
280 for (int i=0; i<depth; i++)
281 c = c.componentType();
282 return c.displayName() + "[]".repeat(depth);
283 }
284 else
285 throw new IllegalStateException(descriptorString());
286 }
287
288 /**
289 * Returns a field type descriptor string for this type
290 *
291 * @return the descriptor string
292 * @jvms 4.3.2 Field Descriptors
293 */
294 String descriptorString();
295
296 /**
297 * Compare the specified object with this descriptor for equality. Returns
298 * {@code true} if and only if the specified object is also a
299 * {@linkplain ClassDesc} and both describe the same type.
300 *
301 * @param o the other object
302 * @return whether this descriptor is equal to the other object
303 */
304 boolean equals(Object o);
305 }