Java精確測量代碼運行時間 代碼執行時間 納秒 nanoTime

Java精確測量代碼運行時間：

        long startTime = System.nanoTime();  //開始時間         for(int i = 0;i<10000;i++){             ;         }         long consumingTime = System.nanoTime() - startTime; //消耗時間         System.out.println(consumingTime);         System.out.println(consumingTime/1000+"微秒");

 

JDK的解釋：

 

public static long nanoTime()

Returns the current value of the most precise available system timer, in nanoseconds.

This method can only be used to measure elapsed time and is not related to any other notion of system or wall-clock time. The value returned represents nanoseconds since some fixed but arbitrary time (perhaps in the future, so values may be negative). This method provides nanosecond precision, but not necessarily nanosecond accuracy. No guarantees are made about how frequently values change. Differences in successive calls that span greater than approximately 292 years (2⁶³ nanoseconds) will not accurately compute elapsed time due to numerical overflow.

For example, to measure how long some code takes to execute:

   long startTime = System.nanoTime();   // ... the code being measured ...   long estimatedTime = System.nanoTime() - startTime; 

返回：

The current value of the system timer, in nanoseconds.

自從：

1.5