1 /*
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  5  * This code is free software; you can redistribute it and/or modify it
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  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  *
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 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.
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 24  */
 25 
 26 package java.lang.reflect;
 27 
 28 import java.util.StringJoiner;
 29 
 30 /**
 31  * The Modifier class provides {@code static} methods and
 32  * constants to decode class and member access modifiers.  The sets of
 33  * modifiers are represented as integers with distinct bit positions
 34  * representing different modifiers.  The values for the constants
 35  * representing the modifiers are taken from the tables in sections
 36  * {@jvms 4.1}, {@jvms 4.4}, {@jvms 4.5}, and {@jvms 4.7} of
 37  * <cite>The Java Virtual Machine Specification</cite>.
 38  *
 39  * @see Class#getModifiers()
 40  * @see Member#getModifiers()
 41  *
 42  * @author Nakul Saraiya
 43  * @author Kenneth Russell
 44  * @since 1.1
 45  */
 46 public class Modifier {
 47     /**
 48      * Do not call.
 49      */
 50     private Modifier() {throw new AssertionError();}
 51 
 52 
 53     /**
 54      * Return {@code true} if the integer argument includes the
 55      * {@code public} modifier, {@code false} otherwise.
 56      *
 57      * @param   mod a set of modifiers
 58      * @return {@code true} if {@code mod} includes the
 59      * {@code public} modifier; {@code false} otherwise.
 60      */
 61     public static boolean isPublic(int mod) {
 62         return (mod & PUBLIC) != 0;
 63     }
 64 
 65     /**
 66      * Return {@code true} if the integer argument includes the
 67      * {@code private} modifier, {@code false} otherwise.
 68      *
 69      * @param   mod a set of modifiers
 70      * @return {@code true} if {@code mod} includes the
 71      * {@code private} modifier; {@code false} otherwise.
 72      */
 73     public static boolean isPrivate(int mod) {
 74         return (mod & PRIVATE) != 0;
 75     }
 76 
 77     /**
 78      * Return {@code true} if the integer argument includes the
 79      * {@code protected} modifier, {@code false} otherwise.
 80      *
 81      * @param   mod a set of modifiers
 82      * @return {@code true} if {@code mod} includes the
 83      * {@code protected} modifier; {@code false} otherwise.
 84      */
 85     public static boolean isProtected(int mod) {
 86         return (mod & PROTECTED) != 0;
 87     }
 88 
 89     /**
 90      * Return {@code true} if the integer argument includes the
 91      * {@code static} modifier, {@code false} otherwise.
 92      *
 93      * @param   mod a set of modifiers
 94      * @return {@code true} if {@code mod} includes the
 95      * {@code static} modifier; {@code false} otherwise.
 96      */
 97     public static boolean isStatic(int mod) {
 98         return (mod & STATIC) != 0;
 99     }
100 
101     /**
102      * Return {@code true} if the integer argument includes the
103      * {@code final} modifier, {@code false} otherwise.
104      *
105      * @param   mod a set of modifiers
106      * @return {@code true} if {@code mod} includes the
107      * {@code final} modifier; {@code false} otherwise.
108      */
109     public static boolean isFinal(int mod) {
110         return (mod & FINAL) != 0;
111     }
112 
113     /**
114      * Return {@code true} if the integer argument includes the
115      * {@code synchronized} modifier, {@code false} otherwise.
116      *
117      * @param   mod a set of modifiers
118      * @return {@code true} if {@code mod} includes the
119      * {@code synchronized} modifier; {@code false} otherwise.
120      */
121     public static boolean isSynchronized(int mod) {
122         return (mod & SYNCHRONIZED) != 0;
123     }
124 
125     /**
126      * Return {@code true} if the integer argument includes the
127      * {@code volatile} modifier, {@code false} otherwise.
128      *
129      * @param   mod a set of modifiers
130      * @return {@code true} if {@code mod} includes the
131      * {@code volatile} modifier; {@code false} otherwise.
132      */
133     public static boolean isVolatile(int mod) {
134         return (mod & VOLATILE) != 0;
135     }
136 
137     /**
138      * Return {@code true} if the integer argument includes the
139      * {@code transient} modifier, {@code false} otherwise.
140      *
141      * @param   mod a set of modifiers
142      * @return {@code true} if {@code mod} includes the
143      * {@code transient} modifier; {@code false} otherwise.
144      */
145     public static boolean isTransient(int mod) {
146         return (mod & TRANSIENT) != 0;
147     }
148 
149     /**
150      * Return {@code true} if the integer argument includes the
151      * {@code native} modifier, {@code false} otherwise.
152      *
153      * @param   mod a set of modifiers
154      * @return {@code true} if {@code mod} includes the
155      * {@code native} modifier; {@code false} otherwise.
156      */
157     public static boolean isNative(int mod) {
158         return (mod & NATIVE) != 0;
159     }
160 
161     /**
162      * Return {@code true} if the integer argument includes the
163      * {@code interface} modifier, {@code false} otherwise.
164      *
165      * @param   mod a set of modifiers
166      * @return {@code true} if {@code mod} includes the
167      * {@code interface} modifier; {@code false} otherwise.
168      */
169     public static boolean isInterface(int mod) {
170         return (mod & INTERFACE) != 0;
171     }
172 
173     /**
174      * Return {@code true} if the integer argument includes the
175      * {@code abstract} modifier, {@code false} otherwise.
176      *
177      * @param   mod a set of modifiers
178      * @return {@code true} if {@code mod} includes the
179      * {@code abstract} modifier; {@code false} otherwise.
180      */
181     public static boolean isAbstract(int mod) {
182         return (mod & ABSTRACT) != 0;
183     }
184 
185     /**
186      * Return {@code true} if the integer argument includes the
187      * {@code strictfp} modifier, {@code false} otherwise.
188      *
189      * @param   mod a set of modifiers
190      * @return {@code true} if {@code mod} includes the
191      * {@code strictfp} modifier; {@code false} otherwise.
192      */
193     public static boolean isStrict(int mod) {
194         return (mod & STRICT) != 0;
195     }
196 
197     /**
198      * Return a string describing the access modifier flags in
199      * the specified modifier. For example:
200      * <blockquote><pre>
201      *    public final synchronized strictfp
202      * </pre></blockquote>
203      * The modifier names are returned in an order consistent with the
204      * suggested modifier orderings given in sections 8.1.1, 8.3.1, 8.4.3, 8.8.3, and 9.1.1 of
205      * <cite>The Java Language Specification</cite>.
206      * The full modifier ordering used by this method is:
207      * <blockquote> {@code
208      * public protected private abstract static final transient
209      * volatile synchronized native strictfp
210      * interface } </blockquote>
211      * The {@code interface} modifier discussed in this class is
212      * not a true modifier in the Java language and it appears after
213      * all other modifiers listed by this method.  This method may
214      * return a string of modifiers that are not valid modifiers of a
215      * Java entity; in other words, no checking is done on the
216      * possible validity of the combination of modifiers represented
217      * by the input.
218      *
219      * Note that to perform such checking for a known kind of entity,
220      * such as a constructor or method, first AND the argument of
221      * {@code toString} with the appropriate mask from a method like
222      * {@link #constructorModifiers} or {@link #methodModifiers}.
223      *
224      * @param   mod a set of modifiers
225      * @return  a string representation of the set of modifiers
226      * represented by {@code mod}
227      */
228     public static String toString(int mod) {
229         StringJoiner sj = new StringJoiner(" ");
230 
231         if ((mod & PUBLIC) != 0)        sj.add("public");
232         if ((mod & PROTECTED) != 0)     sj.add("protected");
233         if ((mod & PRIVATE) != 0)       sj.add("private");
234 
235         /* Canonical order */
236         if ((mod & ABSTRACT) != 0)      sj.add("abstract");
237         if ((mod & STATIC) != 0)        sj.add("static");
238         if ((mod & FINAL) != 0)         sj.add("final");
239         if ((mod & TRANSIENT) != 0)     sj.add("transient");
240         if ((mod & VOLATILE) != 0)      sj.add("volatile");
241         if ((mod & SYNCHRONIZED) != 0)  sj.add("synchronized");
242         if ((mod & NATIVE) != 0)        sj.add("native");
243         if ((mod & STRICT) != 0)        sj.add("strictfp");
244         if ((mod & INTERFACE) != 0)     sj.add("interface");
245 
246         return sj.toString();
247     }
248 
249     /*
250      * Access modifier flag constants from tables 4.1, 4.4, 4.5, and 4.7 of
251      * <cite>The Java Virtual Machine Specification</cite>
252      */
253 
254     /**
255      * The {@code int} value representing the {@code public}
256      * modifier.
257      * @see AccessFlag#PUBLIC
258      */
259     public static final int PUBLIC           = 0x00000001;
260 
261     /**
262      * The {@code int} value representing the {@code private}
263      * modifier.
264      * @see AccessFlag#PRIVATE
265      */
266     public static final int PRIVATE          = 0x00000002;
267 
268     /**
269      * The {@code int} value representing the {@code protected}
270      * modifier.
271      * @see AccessFlag#PROTECTED
272      */
273     public static final int PROTECTED        = 0x00000004;
274 
275     /**
276      * The {@code int} value representing the {@code static}
277      * modifier.
278      * @see AccessFlag#STATIC
279      */
280     public static final int STATIC           = 0x00000008;
281 
282     /**
283      * The {@code int} value representing the {@code final}
284      * modifier.
285      * @see AccessFlag#FINAL
286      */
287     public static final int FINAL            = 0x00000010;
288 
289     /**
290      * The {@code int} value representing the {@code synchronized}
291      * modifier.
292      * @see AccessFlag#SYNCHRONIZED
293      */
294     public static final int SYNCHRONIZED     = 0x00000020;
295 
296     /**
297      * The {@code int} value representing the {@code volatile}
298      * modifier.
299      * @see AccessFlag#VOLATILE
300      */
301     public static final int VOLATILE         = 0x00000040;
302 
303     /**
304      * The {@code int} value representing the {@code transient}
305      * modifier.
306      * @see AccessFlag#TRANSIENT
307      */
308     public static final int TRANSIENT        = 0x00000080;
309 
310     /**
311      * The {@code int} value representing the {@code native}
312      * modifier.
313      * @see AccessFlag#NATIVE
314      */
315     public static final int NATIVE           = 0x00000100;
316 
317     /**
318      * The {@code int} value representing the {@code interface}
319      * modifier.
320      * @see AccessFlag#INTERFACE
321      */
322     public static final int INTERFACE        = 0x00000200;
323 
324     /**
325      * The {@code int} value representing the {@code abstract}
326      * modifier.
327      * @see AccessFlag#ABSTRACT
328      */
329     public static final int ABSTRACT         = 0x00000400;
330 
331     /**
332      * The {@code int} value representing the {@code strictfp}
333      * modifier.
334      * @see AccessFlag#STRICT
335      */
336     public static final int STRICT           = 0x00000800;
337 
338     // Bits not (yet) exposed in the public API either because they
339     // have different meanings for fields and methods and there is no
340     // way to distinguish between the two in this class, or because
341     // they are not Java programming language keywords
342     static final int BRIDGE    = 0x00000040;
343     static final int VARARGS   = 0x00000080;
344     static final int SYNTHETIC = 0x00001000;
345     static final int ANNOTATION  = 0x00002000;
346     static final int ENUM      = 0x00004000;
347     static final int MANDATED  = 0x00008000;
348     static boolean isSynthetic(int mod) {
349       return (mod & SYNTHETIC) != 0;
350     }
351 
352     static boolean isMandated(int mod) {
353       return (mod & MANDATED) != 0;
354     }
355 
356     // Note on the FOO_MODIFIERS fields and fooModifiers() methods:
357     // the sets of modifiers are not guaranteed to be constants
358     // across time and Java SE releases. Therefore, it would not be
359     // appropriate to expose an external interface to this information
360     // that would allow the values to be treated as Java-level
361     // constants since the values could be constant folded and updates
362     // to the sets of modifiers missed. Thus, the fooModifiers()
363     // methods return an unchanging values for a given release, but a
364     // value that can potentially change over time.
365 
366     /**
367      * The Java source modifiers that can be applied to a class.
368      * @jls 8.1.1 Class Modifiers
369      */
370     private static final int CLASS_MODIFIERS =
371         Modifier.PUBLIC         | Modifier.PROTECTED    | Modifier.PRIVATE |
372         Modifier.ABSTRACT       | Modifier.STATIC       | Modifier.FINAL   |
373         Modifier.STRICT;
374 
375     /**
376      * The Java source modifiers that can be applied to an interface.
377      * @jls 9.1.1 Interface Modifiers
378      */
379     private static final int INTERFACE_MODIFIERS =
380         Modifier.PUBLIC         | Modifier.PROTECTED    | Modifier.PRIVATE |
381         Modifier.ABSTRACT       | Modifier.STATIC       | Modifier.STRICT;
382 
383 
384     /**
385      * The Java source modifiers that can be applied to a constructor.
386      * @jls 8.8.3 Constructor Modifiers
387      */
388     private static final int CONSTRUCTOR_MODIFIERS =
389         Modifier.PUBLIC         | Modifier.PROTECTED    | Modifier.PRIVATE;
390 
391     /**
392      * The Java source modifiers that can be applied to a method.
393      * @jls 8.4.3  Method Modifiers
394      */
395     private static final int METHOD_MODIFIERS =
396         Modifier.PUBLIC         | Modifier.PROTECTED    | Modifier.PRIVATE |
397         Modifier.ABSTRACT       | Modifier.STATIC       | Modifier.FINAL   |
398         Modifier.SYNCHRONIZED   | Modifier.NATIVE       | Modifier.STRICT;
399 
400     /**
401      * The Java source modifiers that can be applied to a field.
402      * @jls 8.3.1 Field Modifiers
403      */
404     private static final int FIELD_MODIFIERS =
405         Modifier.PUBLIC         | Modifier.PROTECTED    | Modifier.PRIVATE |
406         Modifier.STATIC         | Modifier.FINAL        | Modifier.TRANSIENT |
407         Modifier.VOLATILE;
408 
409     /**
410      * The Java source modifiers that can be applied to a method or constructor parameter.
411      * @jls 8.4.1 Formal Parameters
412      */
413     private static final int PARAMETER_MODIFIERS =
414         Modifier.FINAL;
415 
416     static final int ACCESS_MODIFIERS =
417         Modifier.PUBLIC | Modifier.PROTECTED | Modifier.PRIVATE;
418 
419     /**
420      * Return an {@code int} value OR-ing together the source language
421      * modifiers that can be applied to a class.
422      * @return an {@code int} value OR-ing together the source language
423      * modifiers that can be applied to a class.
424      *
425      * @jls 8.1.1 Class Modifiers
426      * @since 1.7
427      */
428     public static int classModifiers() {
429         return CLASS_MODIFIERS;
430     }
431 
432     /**
433      * Return an {@code int} value OR-ing together the source language
434      * modifiers that can be applied to an interface.
435      * @return an {@code int} value OR-ing together the source language
436      * modifiers that can be applied to an interface.
437      *
438      * @jls 9.1.1 Interface Modifiers
439      * @since 1.7
440      */
441     public static int interfaceModifiers() {
442         return INTERFACE_MODIFIERS;
443     }
444 
445     /**
446      * Return an {@code int} value OR-ing together the source language
447      * modifiers that can be applied to a constructor.
448      * @return an {@code int} value OR-ing together the source language
449      * modifiers that can be applied to a constructor.
450      *
451      * @jls 8.8.3 Constructor Modifiers
452      * @since 1.7
453      */
454     public static int constructorModifiers() {
455         return CONSTRUCTOR_MODIFIERS;
456     }
457 
458     /**
459      * Return an {@code int} value OR-ing together the source language
460      * modifiers that can be applied to a method.
461      * @return an {@code int} value OR-ing together the source language
462      * modifiers that can be applied to a method.
463      *
464      * @jls 8.4.3 Method Modifiers
465      * @since 1.7
466      */
467     public static int methodModifiers() {
468         return METHOD_MODIFIERS;
469     }
470 
471     /**
472      * Return an {@code int} value OR-ing together the source language
473      * modifiers that can be applied to a field.
474      * @return an {@code int} value OR-ing together the source language
475      * modifiers that can be applied to a field.
476      *
477      * @jls 8.3.1 Field Modifiers
478      * @since 1.7
479      */
480     public static int fieldModifiers() {
481         return FIELD_MODIFIERS;
482     }
483 
484     /**
485      * Return an {@code int} value OR-ing together the source language
486      * modifiers that can be applied to a parameter.
487      * @return an {@code int} value OR-ing together the source language
488      * modifiers that can be applied to a parameter.
489      *
490      * @jls 8.4.1 Formal Parameters
491      * @since 1.8
492      */
493     public static int parameterModifiers() {
494         return PARAMETER_MODIFIERS;
495     }
496 }