/*
 * Copyright (c) 2012, 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.util;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

/**
 * An object that may (but need not) hold one or more references to
 * resources that will be released when closed.  Such objects may be
 * used with try-with-resources or related {@code try...finally}
 * constructions that ensure they are closed as soon as they are no
 * longer needed.  Interface {@code MayHoldCloseableResource} indicates that
 * only a minority of usages warrant resource control constructions:
 * those specialized to known resource-bearing instances, or those
 * that must operate in complete generality.
 *
 * <p>For example, most usages of the {@link java.util.stream.Stream}
 * classes operate on data sources such as an array, {@code
 * Collection}, or generator function that do not require or benefit
 * from explicit resource control.  However, some uses of IO channels
 * as data sources do.
 *
 * <p>Annotation {@link HoldsResource} may be used to guide users or static
 * analysis tools to deciding whether resource-control constructions are
 * warranted when using particular instantiations of
 * {@code MayHoldCloseableResource}.
 *
 * @see AutoCloseable
 * @see HoldsResource
 */
public interface MayHoldCloseableResource extends AutoCloseable {
    /**
     * Closes this resource, relinquishing any underlying resources.
     * This method is invoked automatically on objects managed by the
     * {@code try}-with-resources statement.
     *
     * Implementers of this interface are strongly encouraged
     * to make their {@code close} methods idempotent.
     *
     * @see AutoCloseable#close()
     */
    @Override
    void close();

    /**
     * Indicates that a variable holding a {@code MayHoldCloseableResource} or
     * a method returning a {@code MayHoldCloseableResource} definitely does
     * hold a closeable resource.
     */
    @Retention(RetentionPolicy.CLASS)
    @Documented
    @interface HoldsResource { }
}