class.java

gcc的组建

    if (loader == null)
      return ClassLoader.getSystemResource(name);
    return loader.getResource(name);
  }

  /**
   * Get a resource using this class's package using the
   * getClassLoader().getResourceAsStream() method.  If this class was loaded
   * using the system classloader, ClassLoader.getSystemResource() is used
   * instead.
   *
   * <p>If the name you supply is absolute (it starts with a <code>/</code>),
   * then the leading <code>/</code> is removed and it is passed on to
   * getResource(). If it is relative, the package name is prepended, and
   * <code>.</code>'s are replaced with <code>/</code>.
   *
   * <p>The URL returned is system- and classloader-dependent, and could
   * change across implementations.
   *
   * @param resourceName the name of the resource, generally a path
   * @return an InputStream with the contents of the resource in it, or null
   * @throws NullPointerException if name is null
   * @since 1.1
   */
  public InputStream getResourceAsStream(String resourceName)
  {
    String name = resourcePath(resourceName);
    ClassLoader loader = getClassLoader();
    if (loader == null)
      return ClassLoader.getSystemResourceAsStream(name);
    return loader.getResourceAsStream(name);
  }

  private String resourcePath(String resourceName)
  {
    if (resourceName.length() > 0)
      {
	if (resourceName.charAt(0) != '/')
	  {
	    String pkg = getPackagePortion(getName());
	    if (pkg.length() > 0)
	      resourceName = pkg.replace('.','/') + '/' + resourceName;
	  }
	else
	  {
	    resourceName = resourceName.substring(1);
	  }
      }
    return resourceName;
  }

  /**
   * Get the signers of this class. This returns null if there are no signers,
   * such as for primitive types or void.
   *
   * @return the signers of this class
   * @since 1.1
   */
  public native Object[] getSigners ();
  
  /**
   * Set the signers of this class.
   *
   * @param signers the signers of this class
   */
  native void setSigners(Object[] signers);

  /**
   * Get the direct superclass of this class.  If this is an interface,
   * Object, a primitive type, or void, it will return null. If this is an
   * array type, it will return Object.
   *
   * @return the direct superclass of this class
   */
  public native Class getSuperclass ();
  
  /**
   * Return whether this class is an array type.
   *
   * @return whether this class is an array type
   * @since 1.1
   */
  public native boolean isArray ();
  
  /**
   * Discover whether an instance of the Class parameter would be an
   * instance of this Class as well.  Think of doing
   * <code>isInstance(c.newInstance())</code> or even
   * <code>c.newInstance() instanceof (this class)</code>. While this
   * checks widening conversions for objects, it must be exact for primitive
   * types.
   *
   * @param c the class to check
   * @return whether an instance of c would be an instance of this class
   *         as well
   * @throws NullPointerException if c is null
   * @since 1.1
   */
  public native boolean isAssignableFrom (Class c);
 
  /**
   * Discover whether an Object is an instance of this Class.  Think of it
   * as almost like <code>o instanceof (this class)</code>.
   *
   * @param o the Object to check
   * @return whether o is an instance of this class
   * @since 1.1
   */
  public native boolean isInstance (Object o);
  
  /**
   * Check whether this class is an interface or not.  Array types are not
   * interfaces.
   *
   * @return whether this class is an interface or not
   */
  public native boolean isInterface ();
  
  /**
   * Return whether this class is a primitive type.  A primitive type class
   * is a class representing a kind of "placeholder" for the various
   * primitive types, or void.  You can access the various primitive type
   * classes through java.lang.Boolean.TYPE, java.lang.Integer.TYPE, etc.,
   * or through boolean.class, int.class, etc.
   *
   * @return whether this class is a primitive type
   * @see Boolean#TYPE
   * @see Byte#TYPE
   * @see Character#TYPE
   * @see Short#TYPE
   * @see Integer#TYPE
   * @see Long#TYPE
   * @see Float#TYPE
   * @see Double#TYPE
   * @see Void#TYPE
   * @since 1.1
   */
  public native boolean isPrimitive ();
  
  /**
   * Get a new instance of this class by calling the no-argument constructor.
   * The class is initialized if it has not been already. A security check
   * may be performed, with <code>checkMemberAccess(this, Member.PUBLIC)</code>
   * as well as <code>checkPackageAccess</code> both having to succeed.
   *
   * @return a new instance of this class
   * @throws InstantiationException if there is not a no-arg constructor
   *         for this class, including interfaces, abstract classes, arrays,
   *         primitive types, and void; or if an exception occurred during
   *         the constructor
   * @throws IllegalAccessException if you are not allowed to access the
   *         no-arg constructor because of scoping reasons
   * @throws SecurityException if the security check fails
   * @throws ExceptionInInitializerError if class initialization caused by
   *         this call fails with an exception
   */
  public native Object newInstance ()
    throws InstantiationException, IllegalAccessException;

  // We need a native method to retrieve the protection domain, because we
  // can't add fields to java.lang.Class that are accessible from Java.
  private native ProtectionDomain getProtectionDomain0();

  /**
   * Returns the protection domain of this class. If the classloader did not
   * record the protection domain when creating this class the unknown
   * protection domain is returned which has a <code>null</code> code source
   * and all permissions. A security check may be performed, with
   * <code>RuntimePermission("getProtectionDomain")</code>.
   *
   * @return the protection domain
   * @throws SecurityException if the security manager exists and the caller
   * does not have <code>RuntimePermission("getProtectionDomain")</code>.
   * @see RuntimePermission
   * @since 1.2
   */
  public ProtectionDomain getProtectionDomain()
  {
    SecurityManager sm = System.getSecurityManager();
    if (sm != null)
      sm.checkPermission(VMClassLoader.protectionDomainPermission);
    
    ProtectionDomain protectionDomain = getProtectionDomain0();

    if (protectionDomain == null)
      return VMClassLoader.unknownProtectionDomain;
    else
      return protectionDomain;
  }

  /**
   * Return the human-readable form of this Object.  For an object, this
   * is either "interface " or "class " followed by <code>getName()</code>,
   * for primitive types and void it is just <code>getName()</code>.
   *
   * @return the human-readable form of this Object
   */
  public String toString()
  {
    if (isPrimitive())
      return getName();
    return (isInterface() ? "interface " : "class ") + getName();
  }

  /**
   * Returns the desired assertion status of this class, if it were to be
   * initialized at this moment. The class assertion status, if set, is
   * returned; the backup is the default package status; then if there is
   * a class loader, that default is returned; and finally the system default
   * is returned. This method seldom needs calling in user code, but exists
   * for compilers to implement the assert statement. Note that there is no
   * guarantee that the result of this method matches the class's actual
   * assertion status.
   *
   * @return the desired assertion status
   * @see ClassLoader#setClassAssertionStatus(String, boolean)
   * @see ClassLoader#setPackageAssertionStatus(String, boolean)
   * @see ClassLoader#setDefaultAssertionStatus(boolean)
   * @since 1.4
   */
  public boolean desiredAssertionStatus()
  {
    ClassLoader c = getClassLoader();
    Object status;
    if (c == null)
      return VMClassLoader.defaultAssertionStatus();
    if (c.classAssertionStatus != null)
      synchronized (c)
        {
          status = c.classAssertionStatus.get(getName());
          if (status != null)
            return status.equals(Boolean.TRUE);
        }
    else
      {
        status = ClassLoader.systemClassAssertionStatus.get(getName());
        if (status != null)
          return status.equals(Boolean.TRUE);
      }
    if (c.packageAssertionStatus != null)
      synchronized (c)
        {
          String name = getPackagePortion(getName());
          if ("".equals(name))
            status = c.packageAssertionStatus.get(null);
          else
            do
              {
                status = c.packageAssertionStatus.get(name);
                name = getPackagePortion(name);
              }
            while (! "".equals(name) && status == null);
          if (status != null)
            return status.equals(Boolean.TRUE);
        }
    else
      {
        String name = getPackagePortion(getName());
        if ("".equals(name))
          status = ClassLoader.systemPackageAssertionStatus.get(null);
        else
          do
            {
              status = ClassLoader.systemPackageAssertionStatus.get(name);
              name = getPackagePortion(name);
            }
          while (! "".equals(name) && status == null);
        if (status != null)
          return status.equals(Boolean.TRUE);
      }
    return c.defaultAssertionStatus;
  }

  /**
   * Strip the last portion of the name (after the last dot).
   *
   * @param name the name to get package of
   * @return the package name, or "" if no package
   */
  private static String getPackagePortion(String name)
  {
    int lastInd = name.lastIndexOf('.');
    if (lastInd == -1)
      return "";
    return name.substring(0, lastInd);
  }

  /**
   * Perform security checks common to all of the methods that
   * get members of this Class.
   */
  private void memberAccessCheck(int which)
  {
    SecurityManager sm = System.getSecurityManager();
    if (sm != null)
      {
	sm.checkMemberAccess(this, which);
	Package pkg = getPackage();
	if (pkg != null)
	  sm.checkPackageAccess(pkg.getName());
      }
  }
}