Java TimeUnit

Java

1天=？秒

场景

传递时间的场景很常见，还经常需要传毫秒
虽然写成了乘积的形式，但是可读性还是欠佳

Sample
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Thread.sleep(24*60*60*1000);

java.util.concurrent.TimeUnit提供时间粒度的便利转换

实现

TimeUnit是一个枚举类
每个时间单位是一个枚举实例，重写了一组不同时间单位间的转换方法
枚举类也可以定义成员和方法，TimeUnit是一种典型的应用

TimeUnit.java
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public enum TimeUnit {
    NANOSECONDS {
        public long toNanos(long d)   { return d; }
        public long toMicros(long d)  { return d/(C1/C0); }
        public long toMillis(long d)  { return d/(C2/C0); }
        public long toSeconds(long d) { return d/(C3/C0); }
        public long toMinutes(long d) { return d/(C4/C0); }
        public long toHours(long d)   { return d/(C5/C0); }
        public long toDays(long d)    { return d/(C6/C0); }
        public long convert(long d, TimeUnit u) { return u.toNanos(d); }
        int excessNanos(long d, long m) { return (int)(d - (m*C2)); }
    },

    MICROSECONDS {
        public long toNanos(long d)   { return x(d, C1/C0, MAX/(C1/C0)); }
        public long toMicros(long d)  { return d; }
        public long toMillis(long d)  { return d/(C2/C1); }
        public long toSeconds(long d) { return d/(C3/C1); }
        public long toMinutes(long d) { return d/(C4/C1); }
        public long toHours(long d)   { return d/(C5/C1); }
        public long toDays(long d)    { return d/(C6/C1); }
        public long convert(long d, TimeUnit u) { return u.toMicros(d); }
        int excessNanos(long d, long m) { return (int)((d*C1) - (m*C2)); }
    },

    //...
}

除了转换方法外，还提供了通用的包装方法wait,join,sleep
可以看出对底层方法进行了包装，调用了枚举类的转换函数转成毫秒

TimeUnit.java
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public void timedWait(Object obj, long timeout)
        throws InterruptedException {
    if (timeout > 0) {
        long ms = toMillis(timeout);
        int ns = excessNanos(timeout, ms);
        obj.wait(ms, ns);
    }
}

public void timedJoin(Thread thread, long timeout)
        throws InterruptedException {
    if (timeout > 0) {
        long ms = toMillis(timeout);
        int ns = excessNanos(timeout, ms);
        thread.join(ms, ns);
    }
}

public void sleep(long timeout) throws InterruptedException {
    if (timeout > 0) {
        long ms = toMillis(timeout);
        int ns = excessNanos(timeout, ms);
        Thread.sleep(ms, ns);
    }
}

使用

  • 休眠3秒
Sample
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TimeUnit.SECONDS.sleep(3);
  • 一天的秒数
Sample
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long num = TimeUnit.DAYS.toSeconds(1);

版权声明

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本文永久链接：http://linest.github.io/2018/03/23/java-timeunit/