Profile a stand-alone Java program

[Tarun Trehan]

Hi All,

I have written a simple program that loops through an array and creates some objects.
I would like to know how can profile this program to check for :

Memory Usage

Memory Leaks

I have heard of visualvm as a tool to input a heap dump from applications and analyze.
But, how can i go ahead with a simple JAVA standalone program.
Appreciate your inputs.

/**
 * 
 */
package home.always.learning.java;

import java.text.ParseException;
import java.text.SimpleDateFormat;

/**
 * @author Tarun Trehan
 * @category Utility
 * 
 * Code to validate if input "String" is a valid date or not.
 * In this scenario, there is no fixed format against which the validation is supposed to be done.
 * However, with JAVA , the easiest approach is to catch a Parse Exception.
 * But, for catching a parse exception; we need to test it against a specified format.
 * So, for this implementation, we prepare an array that contains the formats against which we will
 * perform validation test.
 * Next, we loop the entire array and test against each format.
 * If the validation fails, test for other formats till array iteration is completed.
 * If it passes for a given format, break the loop and exit. 
 */

public class MultiFormatDateValidation {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		
		System.out.println("Starting Data Validation Check");
		/* Below Test Case is format and validity test.
		 * 2012 was a leap year and hence 29 is a valid date.
		 * Change year to 2013 and test.
		 */
		
		isDateValid("02/29/2012 00:00:00");
	}
	/*
	 * Core Function for validation check.
	 * 
	 */
	public static boolean isDateValid(String dateValue)
	{
		SimpleDateFormat sdfObj = new SimpleDateFormat();
		sdfObj.setLenient(false);
		boolean returnVal = false;
		/*
		 * Set the permissible formats.
		 * A better approach here would be to define all formats in a .properties file
		 * and load the file during execution.
		 */
		String[] permissFormats = new String[]{"MM/dd/yyyy hh:mm:ss.sss","MM/dd/yyyy hh:mm:ss","yyyy-MM-dd hh:mm:ss.sss","yyyy-MM-dd hh:mm","dd/MM/yyyy",
				"dd-MM-yyyy","MM-dd-yyyy","ddMMyyyy"};
		/*
		 * Loop through array of formats and validate using JAVA API.
		 */
		for (int i = 0; i < permissFormats.length; i++) 
		{
			try
			{
				sdfObj.applyPattern(permissFormats[i]);
				sdfObj.parse(dateValue);
				returnVal = true;
				System.out.println("Looks like a valid date for Date Value :"+dateValue+": For Format:"+permissFormats[i]);
				break;
			}
			catch(ParseException e)
			{
				System.out.println("Parse Exception Occured for Date Value :"+dateValue+":And Format:"+permissFormats[i]);
			}
		}
		return returnVal;
	}
}

[Jeanne Boyarsky]

Your program doesn't run long enough to adequately profile. You could solve this by running it a lot of times in a loop. Or by putting a sleep at the end. The sleep approach would only check for a memory leak as proper memory could get returned by then.

You can still run jhat or visualvm or Eclipse Memory Analyzer against a standalone program. You "just" need to get the process id to take a heap dump or launch visualvm against it. THe "just" is in quotes because you need sufficient time to get the heap dump or look at a visual tool before your program ends. Which goes back to my suggestions above.

[Tarun Trehan]

Thanks Jeanne,

Will add suggested options and go through the visualvm tutorial to profile.

Thanks Again !!!

[Tarun Trehan]

Hi Jeanne/All,

I went through visualvm and tried to profile a simple stand alone program. I was able see increase in memory for the following code:

/**
 * 
 */
package home.always.learning.java;

import java.util.ArrayList;
import java.util.List;

public class Heaper {

	/**
	 * @param args
	 */
	
	private static List<PersonDetails> listObj = new ArrayList<PersonDetails>();
	
	private static final String nameConst = "Tarun Trehan";
	
	public static void main(String[] args)throws Exception{
		personListCreation();
	}
	
	public static void personListCreation() throws Exception
	{
		int i = 0;
		while(true)
		{
			System.out.println("Looping to create person list...");
			i++;
			listObj.add(new PersonDetails(nameConst+i));
			//Thread.sleep(1000L);
		}
	}
}

As expected, memory shoots up and is visible in visualvm snapshot attached i.e. Memory_Shoots.JPG.

However, if i remove the following comment from the code and allow the program to sleep for 1 second; the result is different:

Thread.sleep(1000L);

The memory increases but then stabilizes and it goes on. Please refer Memory_Stabilizes.JPG

I am unable to understand this behavior. Is the sleep giving JVM a chance to remove un referenced objects ? Can you please provide your inputs.

[Tarun Trehan]

Appreciate any help on this ??

[Ulf Dittmer]

What do you mean by "the memory stabilizes"? Memory is consistently allocated in both cases, and every so often reclaimed. Naturally, if the code sleeps most of the time, the rate of increase is a lot slower. In fact, in the second case it's so slow that what you're seeing is not the objects that your code allocates, but the objects the JVM allocates in the course of its normal operation (which is so much more that it entirely obscures your data in the graph).

In the first case it's just a matter of time until the JVM exits with an OutOfMemoryException because its memory allocation is exhausted (because the objects your code allocates can't be reclaimed).

[Tarun Trehan]

Ulf,

Thanks for your input.
I ran the program with

Thread.sleep

for much longer period of time and was able to see the increase in heap.
Appreciate your inputs.