This object indicates the last time - in milliseconds - at which the peak memory usage statistic of this memory pool was reset to the current memory usage. This corresponds to a time stamp as returned by java.lang.System.currentTimeMillis(); Setting this object to a time earlier than its current time value has no effect. Setting this object to a time later than its current time value causes the peak memory usage statistic of this memory pool to be reset to the current memory usage. The new value of this object will be the time at which the reset operation is triggered. There could be a delay between the time at which the reset operation is triggered and the time at which the actual resetting happens, so this value is only indicative. See java.lang.management.MemoryPoolMXBean.resetPeakUsage()