How can I analyze which method consumes more time in java, eclipse, junit?

Question

This may be a dumb question for some professional coders, but I'm going crazy right now, so I'm still asking. Please guide me in the right direction.

How can I analyze which method / partOfMethod consumes more time in my java program?

(I use Eclipse and Junit)

Answer 1

Use jvisualvm. It currently ships with the JDK, but there is a standalone version that is more up to date. As a rule, at startup you can choose which launch of the Java process to connect to (this may be our unit test launch). You can specify which class class filters you need for tracking. Typically, some class equipment will run, and you can track the processing time allocated for each method (also the total time).

Answer 2

You need to get a Java profiler . Some of them integrate well into Eclipse .

In addition, you only need to use your own profiler class (if you do not have a lot of profiling, and if you already suspect some bottlenecks).

Here is a simple class:

/** * Small helper class to profile the code, take timing, ... * * To use this, simply call the start method with an identifier. When you want to measure the time, call the stop method * with the same identifier. To output statistics, simply call the toString method or the toCsv method to create a CSV * file with the profiler information. * * @author Vincent Prat @ MarvinLabs */ public class Profiler { private static final int THEORETICAL_MAX_NAME_LENGTH = 50; private static Profiler singletonInstance = null; private Map<String, Profile> profiles; // Fast access to profiles by name private List<Profile> profilesStack; // Profiles as created chronologically /** * Get access to the singleton instance (create it if necessary) */ public static Profiler getInstance() { if (singletonInstance == null) { singletonInstance = new Profiler(); } return singletonInstance; } /** * Protected constructor for singleton */ protected Profiler() { profiles = new HashMap<String, Profiler.Profile>(); profilesStack = new ArrayList<Profile>(); } /** * Start a profile. If the profile does not exist, it will be created. If it exists, a new round of measure is * taken. * * @param name * The name of the profile. If possible, less than Profiler.THEORETICAL_MAX_NAME_LENGTH characters * * @see Profiler.THEORETICAL_MAX_NAME_LENGTH */ public void start(String name) { Profile p = profiles.get(name); if (p == null) { p = new Profile(name); profiles.put(name, p); profilesStack.add(p); } p.start(); } /** * Stop a profile and compute some statistics about it. * * @param name * The name of the profile as declared in the corresponding start method */ public void stop(String name) { Profile p = profiles.get(name); if (p == null) { throw new RuntimeException("The profile " + name + " has not been created by a call to the start() method!"); } p.stop(); } /** * Clear all the current measures. Not to be called within any start/stop pair. */ public void reset() { profiles.clear(); } /** * Build a string containing all the information about the measures we have taken so far. */ @Override public String toString() { final StringBuffer sb = new StringBuffer(); for (Profile p : profilesStack) { sb.append(p.toString()); sb.append("\n"); } return sb.toString(); } /** * Output the measures to an output string */ public void toCsvFile(OutputStream os) throws IOException { Profile.writeCsvHeader(os); for (Profile p : profilesStack) { p.writeCsvLine(os); } } /** * Profile information. It stores statistics per named profile. * * @author Vincent Prat @ MarvinLabs */ private static class Profile { private static final String CSV_HEADERS = "Name, Call Count, Total Time (ms), Average Time (ms), Min Time (ms), Max Time (ms), Delta Time (ms), Delta Ratio (%)\n"; private static final String FORMAT_STRING = "%-" + THEORETICAL_MAX_NAME_LENGTH + "." + THEORETICAL_MAX_NAME_LENGTH + "s: %3d calls, total %5d ms, avg %5d ms, min %5d ms, max %5d ms, delta %5d ms (%d%%)"; private static final String CSV_FORMAT_STRING = "%s,%d,%d,%d,%d,%d,%d,%d\n"; private String name; private long startTime; private long callCount; private long totalTime; private long minTime; private long maxTime; public Profile(String name) { this.name = name; this.callCount = 0; this.totalTime = 0; this.startTime = 0; this.minTime = Long.MAX_VALUE; this.maxTime = Long.MIN_VALUE; } public void start() { startTime = System.currentTimeMillis(); } public void stop() { final long elapsed = (System.currentTimeMillis() - startTime); if (elapsed < minTime) minTime = elapsed; if (elapsed > maxTime) maxTime = elapsed; totalTime += elapsed; callCount++; } private String getFormattedStats(String format) { final long avgTime = callCount == 0 ? 0 : (long) totalTime / callCount; final long delta = maxTime - minTime; final double deltaRatio = avgTime == 0 ? 0 : 100.0 * ((double) 0.5 * delta / (double) avgTime); return String .format(format, name, callCount, totalTime, avgTime, minTime, maxTime, delta, (int) deltaRatio); } @Override public String toString() { return getFormattedStats(FORMAT_STRING); } public static void writeCsvHeader(OutputStream os) throws IOException { os.write(CSV_HEADERS.getBytes()); } public void writeCsvLine(OutputStream os) throws IOException { os.write(getFormattedStats(CSV_FORMAT_STRING).getBytes()); } } } 

And an example of use:

 Profiler.getInstance().start("marker1"); // Do something... Profiler.getInstance().start("marker2"); // Something else... Profiler.getInstance().stop("marker2"); // And some more... Profiler.getInstance().stop("marker1"); // Output the profiling result System.out.println(Profiler.getInstance().toString()); 

Answer 3

Call me old-fashioned, but this is the easiest approach, in my opinion:

 long a, b, c, d; a = System.currentTimeMillis(); // some code 1 b = System.currentTimeMillis(); // some code 2 c = System.currentTimeMillis(); // some code 3 d = System.currentTimeMillis(); System.out.println("Some code 1 took "+(ba)+"mil to execute. ("+((ba)/1000)+" seconds)"); System.out.println("Some code 2 took "+(cb)+"mil to execute. ("+((cb)/1000)+" seconds)"); System.out.println("Some code 3 took "+(dc)+"mil to execute. ("+((dc)/1000)+" seconds)"); 

Hope this helps :)

Answer 4

There are some online tools, such as IdeOne , which gives the time taken to execute a block of code. Give it a try!

Answer 5

The process of measuring how much of the programming takes runtime is called "profiling."

There are many profiling plugins for eclipse. It is described here .

Answer 6

You can watch Yourkit (commercial software) that can control memory, processor, and more. It has a special view showing how much time was spent on methods (for example, you can see that 40% of the execution time was spent in the xyz() method).