com.wl4g.infra.common.lang.FastTimeClock Maven / Gradle / Ivy
/*
* Copyright 2017 ~ 2025 the original author or authors. James Wong
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.wl4g.infra.common.lang;
/**
* {@link FastTimeClock}
*
* This class is used to solve the problem under the performance of calling
* {@link java.lang.System#currentTimeMillis()} in some OS platform kernels, and
* quickly calculate the current absolute milliseconds by using the relative
* nanosecond time and initial gap of the JVM
*
* @author James Wong <[email protected]>
* @version 2021-09-17 v1.0.0
* @since v1.0.0
* @see https://stackoverflow.com/questions/510462/is-system-nanotime-completely-useless
*/
public abstract class FastTimeClock {
/**
* The difference between any absolute time and relative nanosecond time at
* JVM startup.
*/
private static final long vmTimeDiff = (long) (System.currentTimeMillis() - System.nanoTime() / 100_0000);
public static long currentTimeMillis() {
return (long) ((System.nanoTime() / 100_0000) + vmTimeDiff);
}
}