java ThreadLocal多线程专属的变量源码

package com.geekbang.threadlocal; import java.util.ArrayList; import java.util.List; public class PerformanceTracker { private static class Phase { public Phase(String name, long duration) { this.name = name; this.duration = duration; } private String name; private long duration; @Override public String toString() { return "Phase{" + "name='" + name + '\'' + ", duration=" + duration + "}\n"; } } // TODO ThreadLocal一般都是 static的 // TODO 这样使用ThreadLocal，这些数据不用在应用程序之间传递，而且还可以为每个线程保留自己的一份数据 private static final ThreadLocal<List<Phase>> PHASES = new ThreadLocal<>(); private static final ThreadLocal<Long> PHASE_START_TIME = new ThreadLocal<>(); public static void reset() { PHASES.set(new ArrayList<>()); PHASE_START_TIME.set(-1L); } public static void startPhase() { PHASE_START_TIME.set(System.currentTimeMillis()); } public static void endPhase(String phaseName) { long start = PHASE_START_TIME.get(); PHASES.get().add(new Phase(phaseName, System.currentTimeMillis() - start)); } public static void finish() { List<Phase> phases = PHASES.get(); PHASES.set(null); PHASE_START_TIME.set(null); StringBuilder out = new StringBuilder("------Thread Execution Phase Durations---------\n"); phases.forEach(out::append); out.append("--------------------------------------\n"); System.out.println(out.toString()); } }