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      1 /*
      2  * Copyright 2014 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 android.hardware.camera2.cts.helpers;
     18 
     19 import java.io.Closeable;
     20 import java.io.IOException;
     21 
     22 /**
     23  * Helper set of methods for dealing with objects that are sometimes {@code null}.
     24  *
     25  * <p>Used to remove common patterns like: <pre>{@code
     26  * if (obj != null) {
     27  *     obj.doSomething();
     28  * }</pre>
     29  *
     30  * If this is common, consider adding {@code doSomething} to this class so that the code
     31  * looks more like <pre>{@code
     32  * MaybeNull.doSomething(obj);
     33  * }</pre>
     34  */
     35 public class MaybeNull {
     36     /**
     37      * Close the underlying {@link AutoCloseable}, if it's not {@code null}.
     38      *
     39      * @param closeable An object which implements {@link AutoCloseable}.
     40      * @throws Exception If {@link AutoCloseable#close} fails.
     41      */
     42     public static <T extends AutoCloseable> void close(T closeable) throws Exception {
     43         if (closeable != null) {
     44             closeable.close();
     45         }
     46     }
     47 
     48     /**
     49      * Close the underlying {@link UncheckedCloseable}, if it's not {@code null}.
     50      *
     51      * <p>No checked exceptions are thrown. An unknown runtime exception might still
     52      * be raised.</p>
     53      *
     54      * @param closeable An object which implements {@link UncheckedCloseable}.
     55      */
     56     public static <T extends UncheckedCloseable> void close(T closeable) {
     57         if (closeable != null) {
     58             closeable.close();
     59         }
     60     }
     61 
     62     /**
     63      * Close the underlying {@link Closeable}, if it's not {@code null}.
     64      *
     65      * @param closeable An object which implements {@link Closeable}.
     66      * @throws Exception If {@link Closeable#close} fails.
     67      */
     68     public static <T extends Closeable> void close(T closeable) throws IOException {
     69         if (closeable != null) {
     70             closeable.close();
     71         }
     72     }
     73 
     74     // Suppress default constructor for noninstantiability
     75     private MaybeNull() { throw new AssertionError(); }
     76 }
     77