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Performance and timing in Java Print pdf417 2d barcode in Java Performance and timing

12.8 Performance and timing use jdk barcode pdf417 encoding toembed pdf417 with java What is GS1 DataBar There are some optimization pdf417 for Java steps that you can make to improve the performance of your programs. For example, if you are sure that you will not be overriding a method then you should you use the modi er final. The compiler can then inline the method and the interpreter will not have to search for possible overriding methods.

Inline puts the program code directly in the execution ow and therefore avoids jumping to and from another section of memory. When you are unsure about the relative speed of different coding techniques, you can test them with the static method System.currentTimeMillis().

This method returns a long value equal to the number of milliseconds since a standard date in 1970. That number in itself is of little value, but the difference between two millisecond time readings can be meaningful. Thus, you can bracket a code section of interest with this method and nd the difference in milliseconds to get an idea of how long that section of code takes to run.

Note that on today s high-performance machines, you often need to loop over an operation a large number of times to produce a time in the millisecond range. Such a timing measurement has come to be known as a microbenchmark and is fraught with dif culties for a variety of reasons, including just-intime and dynamic compilation techniques, compilation warm-up periods, the use of separate compile threads, background compilation, compiler optimizations, dead code removal, and others. Nevertheless, many people still rely on System.

currentTimeMillis() to measure execution time differences. We explain here how that is normally done and attempt to ameliorate many of the concerns that make microbenchmarks untrustworthy. With multiprocessing happening in the operating system and multithreading in the JVM, the measured times will vary from run to run, so a statistical average is more meaningful than a single run.

It is wise to unload any unnecessary programs that might steal time slices away from the program you are testing. As an example, consider the java.util.

Vector class we discussed in 10. It is often very useful compared to a regular xed-length array because of Vector s ability to remove and add elements. However, in situations where high performance is required, you may nd that an array is preferable because Vector offers noticeably slower performance than an array.

One reason that Vector is slow is because it is synchronized for thread safety. An alternative that can be used in most situations is the ArrayList class which does not have the synchronization overhead. In the test code below we compare timings of object arrays, Vectors, and ArrayList objects.

For consistency, we populate each with Integer objects. In the main() method shown below in the class TimeTest, we read in some command line parameters and then call doTests() several times. Inside doTests() we call four methods that test fetching Integer objects from four different container types Vector, ArrayList, regular object arrays, and an ArrayList<Integer> collection object that takes advantage of the new generics feature in Java 5.

0 (see 10). If you want to run this code on a pre-5.0 Java system, you ll need to comment out the generics version.

. More techniques and tips import java.util.*;.

public class TimeTest private int fWarmup, fNum, f swing barcode pdf417 Outer, fSleep;. public TimeTest (int warmup, int sleep, int num, int outer) { fWarmup = warmup; fSleep = sleep; fNum = num; fOuter = outer; } // ctor. public static void main (Str servlet barcode pdf417 ing[] args) { int warmup=0, sleep=0, num=0, outer=0, total=0; if (args.length == 5) { warmup = Integer.parseInt (args[0]); sleep num.

= Integer.parseInt (args[1]) ; = Integer.parseInt (args[2]); outer = Integer.

parseInt (args[3]); total = Integer.parseInt (args[4]); System.out.

println ("Testing with warmup = " + warmup + ", sleep = " + sleep + ", num = " + num + ", outer = " + outer + ", total = " + total);. } else { System.err.println jdk pdf417 ("Usage: java TimeTest warmup " + "sleep loop outer total"); System.

exit (1); }. System.out.println ("V\tAL\t AL<I>\tarray"); TimeTest tt = new TimeTest (warmup, sleep, num, outer); for (int i = 0; i < total; i++) { tt.

doTests (); } } // main.
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