org.arbeitspferde.groningen.utility.PinnedClock.java Source code

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Here is the source code for org.arbeitspferde.groningen.utility.PinnedClock.java

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/* Copyright 2012 Google, Inc.
 *
 * 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.arbeitspferde.groningen.utility;

import com.google.common.base.Optional;

import org.joda.time.Instant;

import java.util.concurrent.atomic.AtomicLong;

/**
 * This is merely a {@link Clock} that is useful for testing contexts.
 */
public class PinnedClock implements Clock {
    private static final Optional<Long> noMutation = Optional.of(0L);

    private final AtomicLong time;
    private final Optional<Long> incrementQueryBy;

    /**
     * @param time The time at which this clock shall report.
     */
    public PinnedClock(final long time) {
        this.time = new AtomicLong(time);
        incrementQueryBy = Optional.absent();
    }

    /**
     * @param time The initial time at which this clock shall report.
     * @param incrementQueryBy The amount by which the clock will be mutated on each query for time.
     */
    public PinnedClock(final long time, final long incrementQueryBy) {
        this.time = new AtomicLong(time);
        this.incrementQueryBy = Optional.of(incrementQueryBy);
    }

    @Override
    public Instant now() {
        try {
            return new Instant(time.get());
        } finally {
            time.addAndGet(incrementQueryBy.or(noMutation).get());
        }
    }
}