StopWatch是位于org.springframework.util包下的一個(gè)工具類，通過它可方便的對(duì)程序部分代碼進(jìn)行計(jì)時(shí)(ms級(jí)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(shí)，會(huì)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(shí):" + (end - start)); System.out.println("某某2執(zhí)行耗時(shí):" + (end2 - start2));} |
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運(yùn)行結(jié)果：某某1執(zhí)行耗時(shí):105某某2執(zhí)行耗時(shí):203 |
該種方法通過獲取執(zhí)行完成時(shí)間與執(zhí)行開始時(shí)間的差值得到程序的執(zhí)行時(shí)間，簡(jiǎn)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(shí)，會(huì)更加的讓人忍不住多寫幾個(gè)bug聊表敬意，而且該結(jié)果也不夠直觀，此時(shí)會(huì)想是否有一個(gè)工具類，提供了這些方法，或者自己寫個(gè)工具類，剛好可以滿足這種場(chǎng)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(shí)間點(diǎn)
- 記錄結(jié)束時(shí)間點(diǎn)
- 輸出執(zhí)行時(shí)間及各個(gè)時(shí)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(gè)工具類StopWatch,通過該工具類，我們對(duì)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(shí)，以及執(zhí)行時(shí)間百分比，瞬間感覺比之前的方式高大上了一個(gè)檔次。
除此之外，還有以下兩個(gè)方法shortSummary,getTotalTimeMillis，查看程序執(zhí)行時(shí)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(shí)以上內(nèi)容在該工具類中實(shí)現(xiàn)也極其簡(jiǎn)單，通過start與stop方法分別記錄開始時(shí)間與結(jié)束時(shí)間，其中在記錄結(jié)束時(shí)間時(shí)，會(huì)維護(hù)一個(gè)鏈表類型的tasklist屬性，從而使該類可記錄多個(gè)任務(wù)，最后的輸出也僅僅是對(duì)之前記錄的信息做了一個(gè)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(diǎn)：
優(yōu)點(diǎn)：
- spring自帶工具類，可直接使用
- 代碼實(shí)現(xiàn)簡(jiǎn)單，使用更簡(jiǎn)單
- 統(tǒng)一歸納，展示每項(xiàng)任務(wù)耗時(shí)與占用總時(shí)間的百分比，展示結(jié)果直觀性能消耗相對(duì)較小，并且最大程度的保證了start與stop之間的時(shí)間記錄的準(zhǔn)確性
- 可在start時(shí)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(diǎn)：
- 一個(gè)StopWatch實(shí)例一次只能開啟一個(gè)task，不能同時(shí)start多個(gè)task，并且在該task未stop之前不能start一個(gè)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(gè)，需要new不同的StopWatch實(shí)例
- 代碼侵入式使用，需要改動(dòng)多處代碼
spring中StopWatch源碼實(shí)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
