1 /* 2 * Copyright (C) 2011 The Guava Authors 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.google.common.base; 18 19 import com.google.common.annotations.Beta; 20 import com.google.common.annotations.GwtCompatible; 21 22 /** 23 * A time source; returns a time value representing the number of nanoseconds elapsed since some 24 * fixed but arbitrary point in time. Note that most users should use {@link Stopwatch} instead of 25 * interacting with this class directly. 26 * 27 * <p><b>Warning:</b> this interface can only be used to measure elapsed time, not wall time. 28 * 29 * @author Kevin Bourrillion 30 * @since 10.0 31 * (<a href="http://code.google.com/p/guava-libraries/wiki/Compatibility" 32 * >mostly source-compatible</a> since 9.0) 33 */ 34 @Beta 35 @GwtCompatible 36 public abstract class Ticker { 37 /** 38 * Constructor for use by subclasses. 39 */ Ticker()40 protected Ticker() {} 41 42 /** 43 * Returns the number of nanoseconds elapsed since this ticker's fixed 44 * point of reference. 45 */ read()46 public abstract long read(); 47 48 /** 49 * A ticker that reads the current time using {@link System#nanoTime}. 50 * 51 * @since 10.0 52 */ systemTicker()53 public static Ticker systemTicker() { 54 return SYSTEM_TICKER; 55 } 56 57 private static final Ticker SYSTEM_TICKER = new Ticker() { 58 @Override 59 public long read() { 60 return Platform.systemNanoTime(); 61 } 62 }; 63 } 64