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/**
* An object that accurately measures elapsed time: the measured duration between two
* successive readings of “now” in the same process.
*一个精确计算消耗时间的对象：计算在同一进程中两次连续读取当前时间之间持续的时间
*
In contrast, wall time is a reading of “now” as given by a method like
* {
@link System#currentTimeMillis()}, best represented as an {
@link Instant}. Such values
* can be subtracted to obtain a {
@code Duration} (such as by {
@code Duration.between}), but
* doing so does not give a reliable measurement of elapsed time, because wall time readings
* are inherently approximate, routinely affected by periodic clock corrections. Because this class
* (by default) uses {
@link System#nanoTime}, it is unaffected by these changes.
*作为对照，实际时间是读取当前时间，就像System.currentTimeMillis()方法，一瞬间的最好代表。这种值相减可以得到一段时间，但是这样得不到准确的消耗的时间，因为实际时间读取是本质上近似的，
经常受到周期性时钟校正的影响。因为这个类使用System.nanoTime方法，它不受这些变化的影响
*
Use this class instead of direct calls to {@link System#nanoTime} for two reasons:
*用这个类代替直接调用System.nanoTime有两个原因
*
*
The raw {@code long} values returned by {@code nanoTime} are meaningless and unsafe to use
* in any other way than how {@code Stopwatch} uses them.
任何地方使用nanoTime返回的这个原生的long类型的值相对于Stopwatch使用它相比，毫无意义而且不安全
*
An alternative source of nanosecond ticks can be substituted, for example for testing or
* performance reasons, without affecting most of your code.
一个可供选择的资源是时间片段可以被替换，例如为了测试或性能原因，不影响你的大部分代码
*
*
*
Basic usage:
*
*
{@code
* Stopwatch stopwatch = Stopwatch.createStarted();
* doSomething();
* stopwatch.stop(); // optional
*
* Duration duration = stopwatch.elapsed();
*
* log.info(“time: ” + stopwatch); // formatted string like “12.3 ms”
* }
*
*
The state-changing methods are not idempotent; it is an error to start or stop a stopwatch
* that is already in the desired state.
*这个状态更改的方法不是幂等的，开始或停止一个已经处于期望状态的stopwatch对象是一个错误。
*
When testing code that uses this class, use {@link #createUnstarted(Ticker)} or {@link
* #createStarted(Ticker)} to supply a fake or mock ticker. This allows you to simulate any valid
* behavior of the stopwatch.
*当测试代码使用这个类，使用createUnstarted(Ticker)或createStarted(Ticker)提供一个假的或模拟的ticker，这里允许你模拟任何stopwatch有效的行为
*
Note: This class is not thread-safe.
*这个类是非线程安全的。
*
Warning for Android users: a stopwatch with default behavior may not continue to keep
* time while the device is asleep. Instead, create one like this:
*安卓用户的警告：设备休眠的时候stopwatch默认可能不会继续计算。代替的创建一个类似这种的代码：
*
{@code
* Stopwatch.createStarted(
* new Ticker() {
* public long read() {
* return android.os.SystemClock.elapsedRealtimeNanos();
* }
* });
* }
*
* @author Kevin Bourrillion
* @since 10.0
*/
总结：stopwatch主要功能就是两次star和stop调用之间的时间，还可以多次累加、可以重置。非线程安全的。
增加ticker的作用是可以自己替换和实现时间的读取。
发布者：全栈程序员-站长，转载请注明出处：https://javaforall.net/152409.html原文链接：https://javaforall.net
