源码:
public boolean tryAcquire(int permits, long timeout, TimeUnit unit) { long timeoutMicros = max(unit.toMicros(timeout), 0); checkPermits(permits); long microsToWait; synchronized (mutex()) { long nowMicros = stopwatch.readMicros(); if (!canAcquire(nowMicros, timeoutMicros)) { return false; } else { microsToWait = reserveAndGetWaitLength(permits, nowMicros); } } stopwatch.sleepMicrosUninterruptibly(microsToWait); return true; }
意思是,尝试能否在timeout时间内获取permits个许可,第三个参数是timeout的时间单位,是一个enum,例如:
/** * Time unit representing sixty minutes */ HOURS { public long toNanos(long d) { return x(d, C5/C0, MAX/(C5/C0)); } public long toMicros(long d) { return x(d, C5/C1, MAX/(C5/C1)); } public long toMillis(long d) { return x(d, C5/C2, MAX/(C5/C2)); } public long toSeconds(long d) { return x(d, C5/C3, MAX/(C5/C3)); } public long toMinutes(long d) { return x(d, C5/C4, MAX/(C5/C4)); } public long toHours(long d) { return d; } public long toDays(long d) { return d/(C6/C5); } public long convert(long d, TimeUnit u) { return u.toHours(d); } int excessNanos(long d, long m) { return 0; } },