Java tutorial
/* * Copyright (c) 1996, 2019, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.lang.reflect; import java.security.AccessController; import java.util.StringJoiner; import jdk.internal.reflect.LangReflectAccess; import jdk.internal.reflect.ReflectionFactory; /** * The Modifier class provides {@code static} methods and * constants to decode class and member access modifiers. The sets of * modifiers are represented as integers with distinct bit positions * representing different modifiers. The values for the constants * representing the modifiers are taken from the tables in sections 4.1, 4.4, 4.5, and 4.7 of * <cite>The Java™ Virtual Machine Specification</cite>. * * @see Class#getModifiers() * @see Member#getModifiers() * * @author Nakul Saraiya * @author Kenneth Russell * @since 1.1 */ public class Modifier { /* * Bootstrapping protocol between java.lang and java.lang.reflect * packages */ static { ReflectionFactory factory = AccessController .doPrivileged(new ReflectionFactory.GetReflectionFactoryAction()); factory.setLangReflectAccess(new java.lang.reflect.ReflectAccess()); } /** * Return {@code true} if the integer argument includes the * {@code public} modifier, {@code false} otherwise. * * @param mod a set of modifiers * @return {@code true} if {@code mod} includes the * {@code public} modifier; {@code false} otherwise. */ public static boolean isPublic(int mod) { return (mod & PUBLIC) != 0; } /** * Return {@code true} if the integer argument includes the * {@code private} modifier, {@code false} otherwise. * * @param mod a set of modifiers * @return {@code true} if {@code mod} includes the * {@code private} modifier; {@code false} otherwise. */ public static boolean isPrivate(int mod) { return (mod & PRIVATE) != 0; } /** * Return {@code true} if the integer argument includes the * {@code protected} modifier, {@code false} otherwise. * * @param mod a set of modifiers * @return {@code true} if {@code mod} includes the * {@code protected} modifier; {@code false} otherwise. */ public static boolean isProtected(int mod) { return (mod & PROTECTED) != 0; } /** * Return {@code true} if the integer argument includes the * {@code static} modifier, {@code false} otherwise. * * @param mod a set of modifiers * @return {@code true} if {@code mod} includes the * {@code static} modifier; {@code false} otherwise. */ public static boolean isStatic(int mod) { return (mod & STATIC) != 0; } /** * Return {@code true} if the integer argument includes the * {@code final} modifier, {@code false} otherwise. * * @param mod a set of modifiers * @return {@code true} if {@code mod} includes the * {@code final} modifier; {@code false} otherwise. */ public static boolean isFinal(int mod) { return (mod & FINAL) != 0; } /** * Return {@code true} if the integer argument includes the * {@code synchronized} modifier, {@code false} otherwise. * * @param mod a set of modifiers * @return {@code true} if {@code mod} includes the * {@code synchronized} modifier; {@code false} otherwise. */ public static boolean isSynchronized(int mod) { return (mod & SYNCHRONIZED) != 0; } /** * Return {@code true} if the integer argument includes the * {@code volatile} modifier, {@code false} otherwise. * * @param mod a set of modifiers * @return {@code true} if {@code mod} includes the * {@code volatile} modifier; {@code false} otherwise. */ public static boolean isVolatile(int mod) { return (mod & VOLATILE) != 0; } /** * Return {@code true} if the integer argument includes the * {@code transient} modifier, {@code false} otherwise. * * @param mod a set of modifiers * @return {@code true} if {@code mod} includes the * {@code transient} modifier; {@code false} otherwise. */ public static boolean isTransient(int mod) { return (mod & TRANSIENT) != 0; } /** * Return {@code true} if the integer argument includes the * {@code native} modifier, {@code false} otherwise. * * @param mod a set of modifiers * @return {@code true} if {@code mod} includes the * {@code native} modifier; {@code false} otherwise. */ public static boolean isNative(int mod) { return (mod & NATIVE) != 0; } /** * Return {@code true} if the integer argument includes the * {@code interface} modifier, {@code false} otherwise. * * @param mod a set of modifiers * @return {@code true} if {@code mod} includes the * {@code interface} modifier; {@code false} otherwise. */ public static boolean isInterface(int mod) { return (mod & INTERFACE) != 0; } /** * Return {@code true} if the integer argument includes the * {@code abstract} modifier, {@code false} otherwise. * * @param mod a set of modifiers * @return {@code true} if {@code mod} includes the * {@code abstract} modifier; {@code false} otherwise. */ public static boolean isAbstract(int mod) { return (mod & ABSTRACT) != 0; } /** * Return {@code true} if the integer argument includes the * {@code strictfp} modifier, {@code false} otherwise. * * @param mod a set of modifiers * @return {@code true} if {@code mod} includes the * {@code strictfp} modifier; {@code false} otherwise. */ public static boolean isStrict(int mod) { return (mod & STRICT) != 0; } /** * Return a string describing the access modifier flags in * the specified modifier. For example: * <blockquote><pre> * public final synchronized strictfp * </pre></blockquote> * The modifier names are returned in an order consistent with the * suggested modifier orderings given in sections 8.1.1, 8.3.1, 8.4.3, 8.8.3, and 9.1.1 of * <cite>The Java™ Language Specification</cite>. * The full modifier ordering used by this method is: * <blockquote> {@code * public protected private abstract static final transient * volatile synchronized native strictfp * interface } </blockquote> * The {@code interface} modifier discussed in this class is * not a true modifier in the Java language and it appears after * all other modifiers listed by this method. This method may * return a string of modifiers that are not valid modifiers of a * Java entity; in other words, no checking is done on the * possible validity of the combination of modifiers represented * by the input. * * Note that to perform such checking for a known kind of entity, * such as a constructor or method, first AND the argument of * {@code toString} with the appropriate mask from a method like * {@link #constructorModifiers} or {@link #methodModifiers}. * * @param mod a set of modifiers * @return a string representation of the set of modifiers * represented by {@code mod} */ public static String toString(int mod) { StringJoiner sj = new StringJoiner(" "); if ((mod & PUBLIC) != 0) sj.add("public"); if ((mod & PROTECTED) != 0) sj.add("protected"); if ((mod & PRIVATE) != 0) sj.add("private"); /* Canonical order */ if ((mod & ABSTRACT) != 0) sj.add("abstract"); if ((mod & STATIC) != 0) sj.add("static"); if ((mod & FINAL) != 0) sj.add("final"); if ((mod & TRANSIENT) != 0) sj.add("transient"); if ((mod & VOLATILE) != 0) sj.add("volatile"); if ((mod & SYNCHRONIZED) != 0) sj.add("synchronized"); if ((mod & NATIVE) != 0) sj.add("native"); if ((mod & STRICT) != 0) sj.add("strictfp"); if ((mod & INTERFACE) != 0) sj.add("interface"); return sj.toString(); } /* * Access modifier flag constants from tables 4.1, 4.4, 4.5, and 4.7 of * <cite>The Java™ Virtual Machine Specification</cite> */ /** * The {@code int} value representing the {@code public} * modifier. */ public static final int PUBLIC = 0x00000001; /** * The {@code int} value representing the {@code private} * modifier. */ public static final int PRIVATE = 0x00000002; /** * The {@code int} value representing the {@code protected} * modifier. */ public static final int PROTECTED = 0x00000004; /** * The {@code int} value representing the {@code static} * modifier. */ public static final int STATIC = 0x00000008; /** * The {@code int} value representing the {@code final} * modifier. */ public static final int FINAL = 0x00000010; /** * The {@code int} value representing the {@code synchronized} * modifier. */ public static final int SYNCHRONIZED = 0x00000020; /** * The {@code int} value representing the {@code volatile} * modifier. */ public static final int VOLATILE = 0x00000040; /** * The {@code int} value representing the {@code transient} * modifier. */ public static final int TRANSIENT = 0x00000080; /** * The {@code int} value representing the {@code native} * modifier. */ public static final int NATIVE = 0x00000100; /** * The {@code int} value representing the {@code interface} * modifier. */ public static final int INTERFACE = 0x00000200; /** * The {@code int} value representing the {@code abstract} * modifier. */ public static final int ABSTRACT = 0x00000400; /** * The {@code int} value representing the {@code strictfp} * modifier. */ public static final int STRICT = 0x00000800; // Bits not (yet) exposed in the public API either because they // have different meanings for fields and methods and there is no // way to distinguish between the two in this class, or because // they are not Java programming language keywords static final int BRIDGE = 0x00000040; static final int VARARGS = 0x00000080; static final int SYNTHETIC = 0x00001000; static final int ANNOTATION = 0x00002000; static final int ENUM = 0x00004000; static final int MANDATED = 0x00008000; static boolean isSynthetic(int mod) { return (mod & SYNTHETIC) != 0; } static boolean isMandated(int mod) { return (mod & MANDATED) != 0; } // Note on the FOO_MODIFIERS fields and fooModifiers() methods: // the sets of modifiers are not guaranteed to be constants // across time and Java SE releases. Therefore, it would not be // appropriate to expose an external interface to this information // that would allow the values to be treated as Java-level // constants since the values could be constant folded and updates // to the sets of modifiers missed. Thus, the fooModifiers() // methods return an unchanging values for a given release, but a // value that can potentially change over time. /** * The Java source modifiers that can be applied to a class. * @jls 8.1.1 Class Modifiers */ private static final int CLASS_MODIFIERS = Modifier.PUBLIC | Modifier.PROTECTED | Modifier.PRIVATE | Modifier.ABSTRACT | Modifier.STATIC | Modifier.FINAL | Modifier.STRICT; /** * The Java source modifiers that can be applied to an interface. * @jls 9.1.1 Interface Modifiers */ private static final int INTERFACE_MODIFIERS = Modifier.PUBLIC | Modifier.PROTECTED | Modifier.PRIVATE | Modifier.ABSTRACT | Modifier.STATIC | Modifier.STRICT; /** * The Java source modifiers that can be applied to a constructor. * @jls 8.8.3 Constructor Modifiers */ private static final int CONSTRUCTOR_MODIFIERS = Modifier.PUBLIC | Modifier.PROTECTED | Modifier.PRIVATE; /** * The Java source modifiers that can be applied to a method. * @jls8.4.3 Method Modifiers */ private static final int METHOD_MODIFIERS = Modifier.PUBLIC | Modifier.PROTECTED | Modifier.PRIVATE | Modifier.ABSTRACT | Modifier.STATIC | Modifier.FINAL | Modifier.SYNCHRONIZED | Modifier.NATIVE | Modifier.STRICT; /** * The Java source modifiers that can be applied to a field. * @jls 8.3.1 Field Modifiers */ private static final int FIELD_MODIFIERS = Modifier.PUBLIC | Modifier.PROTECTED | Modifier.PRIVATE | Modifier.STATIC | Modifier.FINAL | Modifier.TRANSIENT | Modifier.VOLATILE; /** * The Java source modifiers that can be applied to a method or constructor parameter. * @jls 8.4.1 Formal Parameters */ private static final int PARAMETER_MODIFIERS = Modifier.FINAL; /** * */ static final int ACCESS_MODIFIERS = Modifier.PUBLIC | Modifier.PROTECTED | Modifier.PRIVATE; /** * Return an {@code int} value OR-ing together the source language * modifiers that can be applied to a class. * @return an {@code int} value OR-ing together the source language * modifiers that can be applied to a class. * * @jls 8.1.1 Class Modifiers * @since 1.7 */ public static int classModifiers() { return CLASS_MODIFIERS; } /** * Return an {@code int} value OR-ing together the source language * modifiers that can be applied to an interface. * @return an {@code int} value OR-ing together the source language * modifiers that can be applied to an interface. * * @jls 9.1.1 Interface Modifiers * @since 1.7 */ public static int interfaceModifiers() { return INTERFACE_MODIFIERS; } /** * Return an {@code int} value OR-ing together the source language * modifiers that can be applied to a constructor. * @return an {@code int} value OR-ing together the source language * modifiers that can be applied to a constructor. * * @jls 8.8.3 Constructor Modifiers * @since 1.7 */ public static int constructorModifiers() { return CONSTRUCTOR_MODIFIERS; } /** * Return an {@code int} value OR-ing together the source language * modifiers that can be applied to a method. * @return an {@code int} value OR-ing together the source language * modifiers that can be applied to a method. * * @jls 8.4.3 Method Modifiers * @since 1.7 */ public static int methodModifiers() { return METHOD_MODIFIERS; } /** * Return an {@code int} value OR-ing together the source language * modifiers that can be applied to a field. * @return an {@code int} value OR-ing together the source language * modifiers that can be applied to a field. * * @jls 8.3.1 Field Modifiers * @since 1.7 */ public static int fieldModifiers() { return FIELD_MODIFIERS; } /** * Return an {@code int} value OR-ing together the source language * modifiers that can be applied to a parameter. * @return an {@code int} value OR-ing together the source language * modifiers that can be applied to a parameter. * * @jls 8.4.1 Formal Parameters * @since 1.8 */ public static int parameterModifiers() { return PARAMETER_MODIFIERS; } }