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(jìn)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(jìn)行查看：
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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));} |
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運(yùn)行結(jié)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(jié)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(jié)果更加直觀的展現(xiàn)出來。
首先我們的需求如下：
- 記錄開始時間點
- 記錄結(jié)束時間點
- 輸出執(zhí)行時間及各個時間段的占比
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：
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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());} |
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運(yùn)行結(jié)果：sw.prettyPrint()~~~~~~~~~~~~~~~~~StopWatch 'test': running time (millis) = 308-----------------------------------------ms % Task name-----------------------------------------00104 034% task100204 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(yùn)行代碼及結(jié)果：
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System.out.println("sw.shortSummary()~~~~~~~~~~~~~~~~~");System.out.println(sw.shortSummary());System.out.println("sw.getTotalTimeMillis()~~~~~~~~~~~~~~~~~");System.out.println(sw.getTotalTimeMillis());運(yùn)行結(jié)果sw.shortSummary()~~~~~~~~~~~~~~~~~StopWatch 'test': running time (millis) = 308sw.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(jié)束時間，其中在記錄結(jié)束時間時，會維護(hù)一個鏈表類型的tasklist屬性，從而使該類可記錄多個任務(wù)，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(jié)果更加直觀的展示出來。
StopWatch優(yōu)缺點：
優(yōu)點：
- spring自帶工具類，可直接使用
- 代碼實現(xiàn)簡單，使用更簡單
- 統(tǒng)一歸納，展示每項任務(wù)耗時與占用總時間的百分比，展示結(jié)果直觀性能消耗相對較小，并且最大程度的保證了start與stop之間的時間記錄的準(zhǔn)確性
- 可在start時直接指定任務(wù)名字，從而更加直觀的顯示記錄結(jié)果
缺點：
- 一個StopWatch實例一次只能開啟一個task，不能同時start多個task，并且在該task未stop之前不能start一個新的task，必須在該task stop之后才能開啟新的task，若要一次開啟多個，需要new不同的StopWatch實例
- 代碼侵入式使用，需要改動多處代碼
spring中StopWatch源碼實現(xiàn)如下：
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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; } }} |
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原文鏈接：https://blog.csdn.net/gxs1688/article/details/87185030
