1 /*
2  * Copyright (C) 2020 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 com.android.server.utils;
18 
19 import android.annotation.NonNull;
20 
21 /**
22  * A class that implements Snappable can generate a read-only copy its instances.  A
23  * snapshot is like a clone except that it is only required to support read-only class
24  * methods.  Snapshots are immutable.  Attempts to modify the state of a snapshot throw
25  * {@link UnsupporteOperationException}.
26  * @param <T> The type returned by the snapshot() method.
27  */
28 public interface Snappable<T> {
29 
30     /**
31      * Create an immutable copy of the object, suitable for read-only methods.  A snapshot
32      * is free to omit state that is only needed for mutating methods.
33      */
snapshot()34     @NonNull T snapshot();
35 }
36