# ConcernOf.java

    /*
     * Copyright 2008 Niclas Hedhman. All rights Reserved.
     *
     * Licensed  under the  Apache License,  Version 2.0  (the "License");
     * you may not use  this file  except in  compliance with the License.
     * You may obtain a copy of the License at
     *
     *   http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed  under the  License is distributed on an "AS IS" BASIS,
     * WITHOUT  WARRANTIES OR CONDITIONS  OF ANY KIND, either  express  or
     * implied.
     *
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */
    package org.qi4j.api.concern;

    import org.qi4j.api.concern.internal.ConcernFor;

    /**
     * Base class for Concerns. It introduces a typed "next" pointer
     * that Concerns can use to invoke the next Concern (or mixin) in
     * the chain.
     * <p>
     * Generic Concerns should subclass {@link GenericConcern} instead.
     * </p>
     * <p>
     * Concerns implementations must be thread-safe in their implementation,
     * as multiple threads may share instances.
     * </p>
     */
    public abstract class ConcernOf<T>
    {
        /**
         * The "next" pointer. This points to
         * the next concern in the chain or the mixin
         * to be invoked.
         */
        final
        @ConcernFor
        protected T next = null;
    }