Stop using system Currenttimemillis() takes too long to count. It's too low. Stopwatch is easy to use!

background

You're still using System.currentTimeMillis... Statistics take time ？

For example, the following code ：

/**
 * @author:  Stack leader 
 * @from:  official account Java Technology stack 
 */
@Test
public void jdkWasteTime() throws InterruptedException {
    long start = System.currentTimeMillis();
    Thread.sleep(3000);
    System.out.printf(" Time consuming ：%dms.", System.currentTimeMillis() - start);
}

System.currentTimeMillis... This method of time-consuming statistics is indeed the most used , Because it doesn't have to introduce other JAR package ,JDK You can get , But it has a few inconvenient places to use ：

1） Initial time value needs to be defined , Use the current time for manual calculation ;

2） It is troublesome to count the time consumption of multiple tasks , If start Incorrect assignment may also cause logic problems ;

Is there a better alternative ？ The answer is yes ：StopWatch！

StopWatch

StopWatch It is a time-consuming tool class ：

frequently-used StopWatch There are two types of tool classes ：

• commons-lang3（Apache General toolkit provided ）

• spring-core（Spring Core packages ）

Although the names of the two tool classes are the same , But the usage is quite different , In this article, the stack leader will show you .

commons-lang3 Provided StopWatch

Introduce dependencies

commons-lang3 yes Apache Open source universal Toolkit , Additional introduction required Maven rely on ：

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>${commons-lang3.version}</version>
</dependency>

A simple example

Create a StopWatch Examples are as follows 3 Methods ：

1） Use new keyword

StopWatch sw = new StopWatch();

2） Use create Factory method

StopWatch sw = StopWatch.create();

3） Use createStarted Method

StopWatch sw = StopWatch.createStarted();

This method will not only create an instance , It also starts the timing .

Let's take a simple example ：

//  Create a  StopWatch  Instance and start timing 
StopWatch sw = StopWatch.createStarted();

//  Sleep 1 second 
Thread.sleep(1000);

// 1002ms
System.out.printf(" Time consuming ：%dms.\n", sw.getTime()); 

More usage

Continue with the previous example .

Pause time ：

//  Pause time 
sw.suspend();

Thread.sleep(1000);

// 1000ms
System.out.printf(" The pause took ：%dms.\n", sw.getTime()); 

Because of the pause , So still 1000ms, Dormant after a pause 1000 ms It won't be counted .

Resume timing ：

//  Resume timing 
sw.resume();

Thread.sleep(1000);

// 2001ms
System.out.printf(" Recovery time ：%dms.\n", sw.getTime()); 

Because of the recovery , The result is 2001 ms, Dormant after recovery 1000 ms It was counted .

Stop timing ：

Thread.sleep(1000);

//  Stop timing 
sw.stop();

Thread.sleep(1000);

// 3009ms
System.out.printf(" Total time ：%dms.\n", sw.getTime()); 

Sleep before stopping timing 1000ms, So the result is 3009ms, You can no longer use pause after you stop timing 、 The function is restored .

Reset timing ：

//  Reset timing 
sw.reset();

//  Start timing 
sw.start();

Thread.sleep(1000);

// 1000ms
System.out.printf(" Reset time ：%dms.\n", sw.getTime()); 

Because the reset timer , So when you start counting again, it becomes 1000ms.

All the complete sample source code of this article has been uploaded ：

https://github.com/javastacks/javastack

welcome Star Study , Back Java Examples will be provided above ！ in addition , The latest interview questions have been sorted out , You can Java Interview database Small program online brush questions .

Spring Provided StopWatch

Let's take a simple example ：

//  Create a  StopWatch  example 
StopWatch sw = StopWatch(" official account Java Technology stack ： Test time ");

//  Start timing 
sw.start(" Mission 1");

//  Sleep 1 second 
Thread.sleep(1000);

//  Stop timing 
sw.stop();

// 1002ms
System.out.printf(" Mission 1 Time consuming ：%d%s.\n", sw.getLastTaskTimeMillis(), "ms");

Spring The way to create an instance is new, Start timing , And getting the time manually start、stop.

Continue to add 2 A mission ：

Thread.sleep(1000);

sw.start(" Mission 2");
Thread.sleep(1100);
sw.stop();

// 1100ms.
System.out.printf(" Mission 2 Time consuming ：%d%s.\n", sw.getLastTaskTimeMillis(), "ms");

sw.start(" Mission 3");
Thread.sleep(1200);
sw.stop();

// 1203ms.
System.out.printf(" Mission 3 Time consuming ：%d%s.\n", sw.getLastTaskTimeMillis(), "ms");

// 3.309373456s.
System.out.printf(" Number of tasks ：%s, Total time ：%ss.\n", sw.getTaskCount(), sw.getTotalTimeSeconds());

Spring An important highlight is the support for formatting print results ：

System.out.println(sw.prettyPrint());

Look at the final output ：

But there is one thing that is not friendly , The formatted results are displayed in nanoseconds , And it can't be modified .. Click on the official account ,Java dried food Timely delivery

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Realization principle

Let's have a look at commons-lang3 and Spring The core source code of ：

In fact, they all make use of JDK Medium System System classes to implement , It's just a series of packages .

summary

commons-lang3 Toolkits and Spring In the framework StopWatch Can easily complete the timing and total time of multiple tasks , No more time-consuming manual calculations , Manually calculate if start Assignment errors may also cause errors .

Of course , The above two StopWatch The function of is far more than that introduced by the stack manager , What the stack leader introduced is enough , More can be studied in depth .

All the complete sample source code of this article has been uploaded ：

https://github.com/javastacks/javastack

welcome Star Study , Back Java Examples will be provided above ！

Summarize the advantages and disadvantages of these two timing tool classes ：

1）commons-lang3 Medium StopWatch The usage of is better than Spring The one in is simpler ;

2）commons-lang3 Medium StopWatch Functional ratio Spring Be more flexible in 、 More powerful , Support pause 、 recovery 、 Reset and other functions ;

3）Spring Provide the name of each subtask , And the function of printing results by format , Better for multi task statistics ;

in summary , Personal recommendation commons-lang3 In the kit , More flexible 、 More powerful , If you don't want to introduce additional packages , You can also consider Spring Medium , According to your own system requirements .

therefore , Don't use System.currentTimeMillis... The statistics took time , too low, Share and forward quickly , Standardize ！

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