camera/camera-core/src/main/java/androidx/camera/core/impl/utils/executor/DirectExecutor.java

/*
 * Copyright 2019 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 androidx.camera.core.impl.utils.executor;

import java.util.concurrent.Executor;

/**
 * An {@link Executor} that runs each task in the thread that invokes {@link Executor#execute
 * execute}.
 */
final class DirectExecutor implements Executor {
    private static volatile DirectExecutor sDirectExecutor;

    static Executor getInstance() {
        if (sDirectExecutor != null) {
            return sDirectExecutor;
        }
        synchronized (DirectExecutor.class) {
            if (sDirectExecutor == null) {
                sDirectExecutor = new DirectExecutor();
            }
        }

        return sDirectExecutor;
    }

    @Override
    public void execute(Runnable command) {
        command.run();
    }
}