1 /*
2 * Copyright (C) 2011 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5 * in compliance with the License. You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the License
10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11 * or implied. See the License for the specific language governing permissions and limitations under
12 * the License.
13 */
14
15 package com.google.common.base;
16
17 import com.google.common.annotations.GwtCompatible;
18
19 /**
20 * A time source; returns a time value representing the number of nanoseconds elapsed since some
21 * fixed but arbitrary point in time. Note that most users should use {@link Stopwatch} instead of
22 * interacting with this class directly.
23 *
24 * <p><b>Warning:</b> this interface can only be used to measure elapsed time, not wall time.
25 *
26 * @author Kevin Bourrillion
27 * @since 10.0 (<a href="https://github.com/google/guava/wiki/Compatibility">mostly
28 * source-compatible</a> since 9.0)
29 */
30 @GwtCompatible
31 @ElementTypesAreNonnullByDefault
32 public abstract class Ticker {
33 /** Constructor for use by subclasses. */
34 protected Ticker() {}
35
36 /** Returns the number of nanoseconds elapsed since this ticker's fixed point of reference. */
37 public abstract long read();
38
39 /**
40 * A ticker that reads the current time using {@link System#nanoTime}.
41 *
42 * @since 10.0
43 */
44 public static Ticker systemTicker() {
45 return SYSTEM_TICKER;
46 }
47
48 private static final Ticker SYSTEM_TICKER =
49 new Ticker() {
50 @Override
51 public long read() {
52 return Platform.systemNanoTime();
53 }
54 };
55 }