/**
 * Checks if the given index is in range.  If not, throws an appropriate
 * runtime exception.  This method does *not* check if the index is
 * negative: It is always used immediately prior to an array access,
 * which throws an ArrayIndexOutOfBoundsException if index is negative.
 */
private void rangeCheck(int index) {
    if (index >= size)
        throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
}

// Maps class name to the corresponding lock object when the current
// class loader is parallel capable.
// Note: VM also uses this field to decide if the current class loader
// is parallel capable and the appropriate lock object for class loading.
private final ConcurrentHashMap<String, Object> parallelLockMap;

/**
 * Returns the lock object for class loading operations.
 * For backward compatibility, the default implementation of this method
 * behaves as follows. If this ClassLoader object is registered as
 * parallel capable, the method returns a dedicated object associated
 * with the specified class name. Otherwise, the method returns this
 * ClassLoader object.
 *
 * @param  className
 *         The name of the to-be-loaded class
 *
 * @return the lock for class loading operations
 *
 * @throws NullPointerException
 *         If registered as parallel capable and {@code className} is null
 *
 * @see #loadClass(String, boolean)
 *
 * @since  1.7
 */
protected Object getClassLoadingLock(String className) {
    Object lock = this;
    if (parallelLockMap != null) {
        Object newLock = new Object();
        lock = parallelLockMap.putIfAbsent(className, newLock);
        if (lock == null) {
            lock = newLock;
        }
    }
    return lock;
}

/**
 * Table initialization and resizing control.  When negative, the
 * table is being initialized or resized: -1 for initialization,
 * else -(1 + the number of active resizing threads).  Otherwise,
 * when table is null, holds the initial table size to use upon
 * creation, or 0 for default. After initialization, holds the
 * next element count value upon which to resize the table.
 */
private transient volatile int sizeCtl;