Java中StopWatch的使用示例詳解
stopWatch 是org.springframework.util 包下的一個工具類,使用它可直觀的輸出代碼執(zhí)行耗時,以及執(zhí)行時間百分比。
在未使用這個工具類之前,如果我們需要統(tǒng)計某段代碼的耗時,我們會這樣寫:
public static void main(String[] args) throws InterruptedException { test0(); } public static void test0() throws InterruptedException { long start = System.currentTimeMills(); // do something Thread.sleep(100); long end = System.currentTimeMills(); long start2 = System.currentTimeMills(); // do somethind long end2 = System.currentTimeMills(); 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)); }
如果改用stopWatch 實現(xiàn)的一個示例
public class StopWatchDemo { public static void main(String[] args) throws InterruptedException { 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 someting Thread.sleep(200); sw.stop(); System.out.println("sw.prettyPrint()-------"); System.out.println(sw.prettyPrint()); } }
運行結果如下:
sw.prettyPrint()------
StopWatch 'test': running time (millis) = 310
-----------------------------------------
ms % Task name
-----------------------------------------
00110 035% task1
00200 065% task2
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的時候,會維護一個鏈表類型的taskList 屬性,從而時該類可記錄多個任務,最后的輸出頁僅僅是對之前的記錄信息做了一個統(tǒng)一的歸納輸出。
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; } } }
從代碼上可以看出, 其原理為使用LinkList 來承接歷史任務,使用自身屬性來承接當前的狀態(tài),調用start 的時候初始化自身狀態(tài),使用stop 的時候來結束當前的狀態(tài)然后加入到LinkList中
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