Modifier.java

/* java.lang.reflect.Modifier
   Copyright (C) 1998, 1999, 2001, 2002, 2005, 2008  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
 
GNU Classpath 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 for more details.

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along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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this exception to your version of the library, but you are not
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exception statement from your version. */


package java.lang.reflect;

import gnu.java.lang.CPStringBuilder;

/**
 * Modifier is a helper class with static methods to determine whether an
 * int returned from getModifiers() represents static, public, protected,
 * native, final, etc... and provides an additional method to print
 * out all of the modifiers in an int in order.
 * <p>
 * The methods in this class use the bitmask values in the VM spec to
 * determine the modifiers of an int. This means that a VM must return a
 * standard mask, conformant with the VM spec.  I don't know if this is how
 * Sun does it, but I'm willing to bet money that it is.
 *
 * @author John Keiser
 * @author Tom Tromey (tromey@cygnus.com)
 * @author Eric Blake (ebb9@email.byu.edu)
 * @see Member#getModifiers()
 * @see Method#getModifiers()
 * @see Field#getModifiers()
 * @see Constructor#getModifiers()
 * @see Class#getModifiers()
 * @since 1.1
 */
public class Modifier
{
  /** <STRONG>This constructor really shouldn't be here ... there are no
   * instance methods or variables of this class, so instantiation is
   * worthless.  However, this function is in the 1.1 spec, so it is added
   * for completeness.</STRONG>
   */
  public Modifier()
  {
  }

  /**
   * Public: accessible from any other class.
   */
  public static final int PUBLIC = 0x0001;

  /**
   * Private: accessible only from the same enclosing class.
   */
  public static final int PRIVATE = 0x0002;

  /**
   * Protected: accessible only to subclasses, or within the package.
   */
  public static final int PROTECTED = 0x0004;

  /**
   * Static:<br><ul>
   * <li>Class: no enclosing instance for nested class.</li>
   * <li>Field or Method: can be accessed or invoked without an
   *     instance of the declaring class.</li>
   * </ul>
   */
  public static final int STATIC = 0x0008;

  /**
   * Final:<br><ul>
   * <li>Class: no subclasses allowed.</li>
   * <li>Field: cannot be changed.</li>
   * <li>Method: cannot be overriden.</li>
   * </ul>
   */
  public static final int FINAL = 0x0010;

  /**
   * Synchronized: Method: lock the class while calling this method.
   */
  public static final int SYNCHRONIZED = 0x0020;

  /**
   * Volatile: Field: cannot be cached.
   */
  public static final int VOLATILE = 0x0040;

  /**
   * Transient: Field: not serialized or deserialized.
   */
  public static final int TRANSIENT = 0x0080;

  /**
   * Native: Method: use JNI to call this method.
   */
  public static final int NATIVE = 0x0100;

  /**
   * Interface: Class: is an interface.
   */
  public static final int INTERFACE = 0x0200;

  /**
   * Abstract:<br><ul>
   * <li>Class: may not be instantiated.</li>
   * <li>Method: may not be called.</li>
   * </ul>
   */
  public static final int ABSTRACT = 0x0400;

  /**
   * Strictfp: Method: expressions are FP-strict.<p>
   * Also used as a modifier for classes, to mean that all initializers
   * and constructors are FP-strict, but does not show up in
   * Class.getModifiers.
   */
  public static final int STRICT = 0x0800;


  /**
   * Super - treat invokespecial as polymorphic so that super.foo() works
   * according to the JLS. This is a reuse of the synchronized constant
   * to patch a hole in JDK 1.0. *shudder*.
   */
  static final int SUPER = 0x0020;

  /**
   * All the flags, only used by code in this package.
   */
  static final int ALL_FLAGS = 0xfff;

  /**
   * Flag indicating a bridge method.
   */
  static final int BRIDGE = 0x40;

  /**
   * Flag indicating a varargs method.
   */
  static final int VARARGS = 0x80;

  /**
   * Flag indicating a synthetic member.
   */
  static final int SYNTHETIC = 0x1000;

  /**
   * Flag indicating an enum constant or an enum class.
   */
  static final int ENUM = 0x4000;

  /**
   * Check whether the given modifier is abstract.
   * @param mod the modifier.
   * @return <code>true</code> if abstract, <code>false</code> otherwise.
   */
  public static boolean isAbstract(int mod)
  {
    return (mod & ABSTRACT) != 0;
  }

  /**
   * Check whether the given modifier is final.
   * @param mod the modifier.
   * @return <code>true</code> if final, <code>false</code> otherwise.
   */
  public static boolean isFinal(int mod)
  {
    return (mod & FINAL) != 0;
  }

  /**
   * Check whether the given modifier is an interface.
   * @param mod the modifier.
   * @return <code>true</code> if an interface, <code>false</code> otherwise.
   */
  public static boolean isInterface(int mod)
  {
    return (mod & INTERFACE) != 0;
  }

  /**
   * Check whether the given modifier is native.
   * @param mod the modifier.
   * @return <code>true</code> if native, <code>false</code> otherwise.
   */
  public static boolean isNative(int mod)
  {
    return (mod & NATIVE) != 0;
  }

  /**
   * Check whether the given modifier is private.
   * @param mod the modifier.
   * @return <code>true</code> if private, <code>false</code> otherwise.
   */
  public static boolean isPrivate(int mod)
  {
    return (mod & PRIVATE) != 0;
  }

  /**
   * Check whether the given modifier is protected.
   * @param mod the modifier.
   * @return <code>true</code> if protected, <code>false</code> otherwise.
   */
  public static boolean isProtected(int mod)
  {
    return (mod & PROTECTED) != 0;
  }

  /**
   * Check whether the given modifier is public.
   * @param mod the modifier.
   * @return <code>true</code> if public, <code>false</code> otherwise.
   */
  public static boolean isPublic(int mod)
  {
    return (mod & PUBLIC) != 0;
  }

  /**
   * Check whether the given modifier is static.
   * @param mod the modifier.
   * @return <code>true</code> if static, <code>false</code> otherwise.
   */
  public static boolean isStatic(int mod)
  {
    return (mod & STATIC) != 0;
  }

  /**
   * Check whether the given modifier is strictfp.
   * @param mod the modifier.
   * @return <code>true</code> if strictfp, <code>false</code> otherwise.
   */
  public static boolean isStrict(int mod)
  {
    return (mod & STRICT) != 0;
  }

  /**
   * Check whether the given modifier is synchronized.
   * @param mod the modifier.
   * @return <code>true</code> if synchronized, <code>false</code> otherwise.
   */
  public static boolean isSynchronized(int mod)
  {
    return (mod & SYNCHRONIZED) != 0;
  }

  /**
   * Check whether the given modifier is transient.
   * @param mod the modifier.
   * @return <code>true</code> if transient, <code>false</code> otherwise.
   */
  public static boolean isTransient(int mod)
  {
    return (mod & TRANSIENT) != 0;
  }

  /**
   * Check whether the given modifier is volatile.
   * @param mod the modifier.
   * @return <code>true</code> if volatile, <code>false</code> otherwise.
   */
  public static boolean isVolatile(int mod)
  {
    return (mod & VOLATILE) != 0;
  }

  /**
   * Get a string representation of all the modifiers represented by the
   * given int. The keywords are printed in this order:
   * <code>&lt;public|protected|private&gt; abstract static final transient
   * volatile synchronized native strictfp interface</code>.
   *
   * @param mod the modifier.
   * @return the String representing the modifiers.
   */
  public static String toString(int mod)
  {
    return toString(mod, new CPStringBuilder()).toString();
  }

  /**
   * Package helper method that can take a CPStringBuilder.
   * @param mod the modifier
   * @param r the CPStringBuilder to which the String representation is appended
   * @return r, with information appended
   */
  static CPStringBuilder toString(int mod, CPStringBuilder r)
  {
    if (isPublic(mod))
      r.append("public ");
    if (isProtected(mod))
      r.append("protected ");
    if (isPrivate(mod))
      r.append("private ");
    if (isAbstract(mod))
      r.append("abstract ");
    if (isStatic(mod))
      r.append("static ");
    if (isFinal(mod))
      r.append("final ");
    if (isTransient(mod))
      r.append("transient ");
    if (isVolatile(mod))
      r.append("volatile ");
    if (isSynchronized(mod))
      r.append("synchronized ");
    if (isNative(mod))
      r.append("native ");
    if (isStrict(mod))
      r.append("strictfp ");
    if (isInterface(mod))
      r.append("interface ");
    
    // Trim trailing space.
    if ((mod & ALL_FLAGS) != 0)
      r.setLength(r.length() - 1);
    return r;
  }
}