一、总结
1.1、使用System.currentTimeMillis();计算程序执行毫秒数
// 开始时间1
long startTime1 = System.currentTimeMillis();
Thread.sleep(100);
// 结束时间1
long endTime1 = System.currentTimeMillis();
// 开始时间2
long startTime2 = System.currentTimeMillis();
Thread.sleep(200);
// 结束时间2
long endTime2 = System.currentTimeMillis();
System.out.println("逻辑1执行时间："+ (endTime1 - startTime1));
System.out.println("逻辑2执行时间："+ (endTime2 -startTime2));
1.2、使用org.springframework.util包下的一个工具类StopWatch计算执行时间
StopWatch testTask = new StopWatch("TestTask");
// 记录开始时间点
testTask.start("task1");
Thread.sleep(100);
// 记录结束时间点
testTask.stop();
// 记录开始时间点
testTask.start("task2");
Thread.sleep(200);
// 记录结束时间点
testTask.stop();
// 输出执行时间
System.out.println("==任务执行时间==");
System.out.println(testTask.prettyPrint());
System.out.println("执行任务的毫秒数："+testTask.getTotalTimeMillis());
1.3两个案例的完整代码、执行结果
package time.stopwatch;
import org.springframework.util.StopWatch;
public class StopWatchTest {
public static void main(String[] args) throws InterruptedException {
// 计算执行时间
calculateExecuteTime1();
// 计算执行时间
calculateExecuteTime2();
}
public static void calculateExecuteTime1() throws InterruptedException {
// 开始时间1
long startTime1 = System.currentTimeMillis();
Thread.sleep(100);
// 结束时间1
long endTime1 = System.currentTimeMillis();
// 开始时间2
long startTime2 = System.currentTimeMillis();
Thread.sleep(200);
// 结束时间2
long endTime2 = System.currentTimeMillis();
System.out.println("逻辑1执行时间："+ (endTime1 - startTime1));
System.out.println("逻辑2执行时间："+ (endTime2 -startTime2));
}
public static void calculateExecuteTime2() throws InterruptedException {
StopWatch testTask = new StopWatch("TestTask");
// 记录开始时间点
testTask.start("task1");
Thread.sleep(100);
// 记录结束时间点
testTask.stop();
// 记录开始时间点
testTask.start("task2");
Thread.sleep(200);
// 记录结束时间点
testTask.stop();
// 输出执行时间
System.out.println("==任务执行时间==");
System.out.println(testTask.prettyPrint());
System.out.println("执行任务的毫秒数："+testTask.getTotalTimeMillis());
}
}
执行结果：
逻辑1执行时间：109
逻辑2执行时间：203
==任务执行时间==
StopWatch 'TestTask': running time = 319076700 ns
---------------------------------------------
ns % Task name
---------------------------------------------
114748000 036% task1
204328700 064% task2
执行任务的毫秒数：319
1.4 StopWatch优缺点：
优点：
1、spring自带工具类，可直接使用
2、代码实现简单，使用更简单
3、统一归纳，展示每项任务耗时与占用总时间的百分比，展示结果直观
4、性能消耗相对较小，并且最大程度的保证了start与stop之间的时间记录的准确性
5、可在start时直接指定任务名字，从而更加直观的显示记录结果
缺点：
1、一个StopWatch实例一次只能开启一个task，不能同时start多个task，并且在该task未stop之前不能start一个新的task，必须在该task stop之后才能开启新的task，若要一次开启多个，需要new不同的StopWatch实例
2、代码侵入式使用，需要改动多处代码文章来源：https://www.toymoban.com/news/detail-830579.html
1.5、spring中StopWatch源码实现如下：
import java.text.NumberFormat;
import java.util.LinkedList;
import java.util.List;
public class StopWatch {
private final String id;
private boolean keepTaskList = true;
private final List<TaskInfo> taskList = new LinkedList();
private long startTimeMillis;
private boolean running;
private String currentTaskName;
private StopWatch.TaskInfo lastTaskInfo;
private int taskCount;
private long totalTimeMillis;
public StopWatch() {
this.id = "";
}
public StopWatch(String id) {
this.id = id;
}
public void setKeepTaskList(boolean keepTaskList) {
this.keepTaskList = keepTaskList;
}
public void start() throws IllegalStateException {
this.start("");
}
public void start(String taskName) throws IllegalStateException {
if (this.running) {
throw new IllegalStateException("Can't start StopWatch: it's already running");
} else {
this.startTimeMillis = System.currentTimeMillis();
this.running = true;
this.currentTaskName = taskName;
}
}
public void stop() throws IllegalStateException {
if (!this.running) {
throw new IllegalStateException("Can't stop StopWatch: it's not running");
} else {
long lastTime = System.currentTimeMillis() - this.startTimeMillis;
this.totalTimeMillis += lastTime;
this.lastTaskInfo = new StopWatch.TaskInfo(this.currentTaskName, lastTime);
if (this.keepTaskList) {
this.taskList.add(this.lastTaskInfo);
}
++this.taskCount;
this.running = false;
this.currentTaskName = null;
}
}
public boolean isRunning() {
return this.running;
}
public long getLastTaskTimeMillis() throws IllegalStateException {
if (this.lastTaskInfo == null) {
throw new IllegalStateException("No tasks run: can't get last task interval");
} else {
return this.lastTaskInfo.getTimeMillis();
}
}
public String getLastTaskName() throws IllegalStateException {
if (this.lastTaskInfo == null) {
throw new IllegalStateException("No tasks run: can't get last task name");
} else {
return this.lastTaskInfo.getTaskName();
}
}
public StopWatch.TaskInfo getLastTaskInfo() throws IllegalStateException {
if (this.lastTaskInfo == null) {
throw new IllegalStateException("No tasks run: can't get last task info");
} else {
return this.lastTaskInfo;
}
}
public long getTotalTimeMillis() {
return this.totalTimeMillis;
}
public double getTotalTimeSeconds() {
return (double) this.totalTimeMillis / 1000.0D;
}
public int getTaskCount() {
return this.taskCount;
}
public StopWatch.TaskInfo[] getTaskInfo() {
if (!this.keepTaskList) {
throw new UnsupportedOperationException("Task info is not being kept!");
} else {
return (StopWatch.TaskInfo[]) this.taskList.toArray(new StopWatch.TaskInfo[this.taskList.size()]);
}
}
public String shortSummary() {
return "StopWatch '" + this.id + "': running time (millis) = " + this.getTotalTimeMillis();
}
public String prettyPrint() {
StringBuilder sb = new StringBuilder(this.shortSummary());
sb.append('\n');
if (!this.keepTaskList) {
sb.append("No task info kept");
} else {
sb.append("-----------------------------------------\n");
sb.append("ms % Task name\n");
sb.append("-----------------------------------------\n");
NumberFormat nf = NumberFormat.getNumberInstance();
nf.setMinimumIntegerDigits(5);
nf.setGroupingUsed(false);
NumberFormat pf = NumberFormat.getPercentInstance();
pf.setMinimumIntegerDigits(3);
pf.setGroupingUsed(false);
StopWatch.TaskInfo[] var7;
int var6 = (var7 = this.getTaskInfo()).length;
for (int var5 = 0; var5 < var6; ++var5) {
StopWatch.TaskInfo task = var7[var5];
sb.append(nf.format(task.getTimeMillis())).append(" ");
sb.append(pf.format(task.getTimeSeconds() / this.getTotalTimeSeconds())).append(" ");
sb.append(task.getTaskName()).append("\n");
}
}
return sb.toString();
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder(this.shortSummary());
if (this.keepTaskList) {
StopWatch.TaskInfo[] var5;
int var4 = (var5 = this.getTaskInfo()).length;
for (int var3 = 0; var3 < var4; ++var3) {
StopWatch.TaskInfo task = var5[var3];
sb.append("; [").append(task.getTaskName()).append("] took ").append(task.getTimeMillis());
long percent = Math.round(100.0D * task.getTimeSeconds() / this.getTotalTimeSeconds());
sb.append(" = ").append(percent).append("%");
}
} else {
sb.append("; no task info kept");
}
return sb.toString();
}
public static final class TaskInfo {
private final String taskName;
private final long timeMillis;
TaskInfo(String taskName, long timeMillis) {
this.taskName = taskName;
this.timeMillis = timeMillis;
}
public String getTaskName() {
return this.taskName;
}
public long getTimeMillis() {
return this.timeMillis;
}
public double getTimeSeconds() {
return (double) this.timeMillis / 1000.0D;
}
}
}
原文摘录至：https://blog.csdn.net/gxs1688/article/details/87185030
致敬原作者：一个不二，侵删。文章来源地址https://www.toymoban.com/news/detail-830579.html
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