src/com/android/quicksearchbox/util/NowOrLater.java

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * 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 com.android.quicksearchbox.util;

/**
 * Interface for an object that may be constructed asynchronously. In cases when the object is ready
 * (on constructible) immediately, it provides synchronous access to it. Otherwise, the object can
 * be sent to a {@link Consumer} later.
 */
public interface NowOrLater<C> {

    /**
     * Indicates if the object is ready (or constructible synchronously).
     */
    boolean haveNow();

    /**
     * Gets the object now. Should only be called if {@link #haveNow()} returns {@code true},
     * otherwise an {@link IllegalStateException} will be thrown.
     */
    C getNow();

    /**
     * Request the object asynchronously. This can be called even if the object is ready now, in
     * which case the callback may be made in context. The thread on which the consumer is called
     * back depends on the implementation.
     */
    void getLater(Consumer<? super C> consumer);

}