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小編這次要給大家分享的是如何使用Spring計時器StopWatch，文章內(nèi)容豐富，感興趣的小伙伴可以來了解一下，希望大家閱讀完這篇文章之后能夠有所收獲。
StopWatch是位于org.springframework.util包下的一個工具類，通過它可方便的對程序部分代碼進行計時(ms級別)，適用于同步單線程代碼塊。
正常情況下，我們?nèi)绻枰茨扯未a的執(zhí)行耗時，會通過如下的方式進行查看：
public static void main(String[] args) throws InterruptedException {
StopWatchTest.test0();
// StopWatchTest.test1();
}
public static void test0() throws InterruptedException {
long start = System.currentTimeMillis();
// do something
Thread.sleep(100);
long end = System.currentTimeMillis();
long start2 = System.currentTimeMillis();
// do something
Thread.sleep(200);
long end2 = System.currentTimeMillis();
System.out.println("某某1執(zhí)行耗時:" + (end - start));
System.out.println("某某2執(zhí)行耗時:" + (end2 - start2));
}運行結果：
某某1執(zhí)行耗時:105
某某2執(zhí)行耗時:203
該種方法通過獲取執(zhí)行完成時間與執(zhí)行開始時間的差值得到程序的執(zhí)行時間，簡單直接有效，但想必寫多了也是比較煩人的，尤其是碰到不可描述的代碼時，會更加的讓人忍不住多寫幾個bug聊表敬意，而且該結果也不夠直觀，此時會想是否有一個工具類，提供了這些方法，或者自己寫個工具類，剛好可以滿足這種場景，并且把結果更加直觀的展現(xiàn)出來。
首先我們的需求如下：
根據(jù)該需求，我們可直接使用org.springframework.util包下的一個工具類StopWatch,通過該工具類，我們對上述代碼做如下改造：
public static void main(String[] args) throws InterruptedException {
// StopWatchTest.test0();
StopWatchTest.test1();
}
public static void test1() throws InterruptedException {
StopWatch sw = new StopWatch("test");
sw.start("task1");
// do something
Thread.sleep(100);
sw.stop();
sw.start("task2");
// do something
Thread.sleep(200);
sw.stop();
System.out.println("sw.prettyPrint()~~~~~~~~~~~~~~~~~");
System.out.println(sw.prettyPrint());
}運行結果：
sw.prettyPrint()~~~~~~~~~~~~~~~~~
StopWatch 'test': running time (millis) = 308
-----------------------------------------
ms % Task name
-----------------------------------------
00104 034% task1
00204 066% task2
start開始記錄，stop停止記錄，然后通過StopWatch的prettyPrint方法，可直觀的輸出代碼執(zhí)行耗時，以及執(zhí)行時間百分比，瞬間感覺比之前的方式高大上了一個檔次。
除此之外，還有以下兩個方法shortSummary,getTotalTimeMillis，查看程序執(zhí)行時間。
運行代碼及結果：
System.out.println("sw.shortSummary()~~~~~~~~~~~~~~~~~");
System.out.println(sw.shortSummary());
System.out.println("sw.getTotalTimeMillis()~~~~~~~~~~~~~~~~~");
System.out.println(sw.getTotalTimeMillis());運行結果
sw.shortSummary()~~~~~~~~~~~~~~~~~
StopWatch 'test': running time (millis) = 308
sw.getTotalTimeMillis()~~~~~~~~~~~~~~~~~
308
其實以上內(nèi)容在該工具類中實現(xiàn)也極其簡單，通過start與stop方法分別記錄開始時間與結束時間，其中在記錄結束時間時，會維護一個鏈表類型的tasklist屬性，從而使該類可記錄多個任務，最后的輸出也僅僅是對之前記錄的信息做了一個統(tǒng)一的歸納輸出，從而使結果更加直觀的展示出來。
StopWatch優(yōu)缺點：
優(yōu)點：
缺點：
spring中StopWatch源碼實現(xiàn)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;
}
}
}看完這篇關于如何使用Spring計時器StopWatch的文章，如果覺得文章內(nèi)容寫得不錯的話，可以把它分享出去給更多人看到。
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