Performance: clone() vs. new GregorianCalendar()

Comparação entre quadro formas de utilização de GregorianCalendar.

retirado de link

::Environment::
- JDK "1.6.0" (build 1.6.0-b105)
- Linux (CentOS 4.4)

::Result::

loop	by Clone	by MilliSec	by Setter	by Constructor
100	11ms	11ms	5ms	2ms
1000	59ms	61ms	9ms	6ms
10000	85ms	71ms	59ms	19ms
30000	178ms	136ms	102ms	28ms
60000	279ms	249ms	189ms	42ms

::Code::
By Clone

public long byClone(final int loop) {
 final long start = System.currentTimeMillis();
 for (int i = 0; i < loop; i++) {
   Calendar cal = (Calendar) Calendar.getInstance().clone();
 }
 final long end = System.currentTimeMillis();
 return end - start;
}

By Setting MilliSeconds

public long byMilliSeconds(final int loop) {
 final Calendar now = Calendar.getInstance();
 final TimeZone tz = now.getTimeZone();
 final long mill = now.getTimeInMillis();

 final long start = System.currentTimeMillis();
 for (int i = 0; i < loop; i++) {
   Calendar cal = new GregorianCalendar(tz);
   cal.setTimeInMillis(mill);
 }
 final long end = System.currentTimeMillis();

 return end - start;
}

By Setting Each Field

public long bySetter(final int loop) {
 final Calendar now = Calendar.getInstance();
 final int currentYear = now.get(Calendar.YEAR);
 final int currentMonth = now.get(Calendar.MONTH);
 final int currentDate = now.get(Calendar.DATE);
 final int currentHour = now.get(Calendar.HOUR);
 final int currentMinute = now.get(Calendar.MINUTE);
 final int currentSecond = now.get(Calendar.SECOND);
 final int currentMilliSecond = now.get(Calendar.MILLISECOND);
 final TimeZone tz = now.getTimeZone();

 final long start = System.currentTimeMillis();
 for (int i = 0; i < loop; i++) {
   Calendar cal = new GregorianCalendar(tz);
   cal.set(currentYear, currentMonth, currentDate, currentHour, currentMinute, currentSecond);
   cal.set(Calendar.MILLISECOND, currentMilliSecond);
 }
 final long end = System.currentTimeMillis();

 return end - start;
}

By Constructor

public long byConstructor(final int loop) {
 final Calendar now = Calendar.getInstance();
 final int currentYear = now.get(Calendar.YEAR);
 final int currentMonth = now.get(Calendar.MONTH);
 final int currentDate = now.get(Calendar.DATE);
 final int currentHour = now.get(Calendar.HOUR);
 final int currentMinute = now.get(Calendar.MINUTE);
 final int currentSecond = now.get(Calendar.SECOND);
 final int currentMilliSecond = now.get(Calendar.MILLISECOND);
 final TimeZone tz = now.getTimeZone();

 final long start = System.currentTimeMillis();
 for (int i = 0; i < loop; i++) {
   Calendar cal = new GregorianCalendar(currentYear, currentMonth, currentDate, currentHour, currentMinute, currentSecond);
   cal.set(Calendar.MILLISECOND, currentMilliSecond);
   cal.setTimeZone(tz);
 }
 final long end = System.currentTimeMillis();

 return end - start;
}