1 /*
2  * Copyright 2019 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package androidx.camera.core.impl.utils.executor;
18 
19 import java.util.concurrent.Executor;
20 
21 /**
22  * An {@link Executor} that runs each task in the thread that invokes {@link Executor#execute
23  * execute}.
24  */
25 final class DirectExecutor implements Executor {
26     private static volatile DirectExecutor sDirectExecutor;
27 
getInstance()28     static Executor getInstance() {
29         if (sDirectExecutor != null) {
30             return sDirectExecutor;
31         }
32         synchronized (DirectExecutor.class) {
33             if (sDirectExecutor == null) {
34                 sDirectExecutor = new DirectExecutor();
35             }
36         }
37 
38         return sDirectExecutor;
39     }
40 
41     @Override
execute(Runnable command)42     public void execute(Runnable command) {
43         command.run();
44     }
45 }
46