Medir o tempo de execução de um método

Programação Java
#1

Como faço para medir o tempo de execução de um método?

Exemplo

TempoInicial // captura o tempo do sistema

metodoQualquer();

TempoFinal //captura o tempo do sistema

TempoExecucao = TempoFinal - TempoInicial;

#2 
long tempoInicial = System.currentTimeMillis();

// execução do método

System.out.println("o metodo executou em " + System.currentTimeMillis() - tempoInicial);
1 curtida
#3

Gustavo,

Para medir:

long start = System.currentTimeMillis();

// faz o trabalho a ser medido

long elapsed = System.currentTimeMillis() - start;

Com isso, você tem o tempo gasto em milissegundos. Para ver em segundos, divida por 1000, em minutos, por 60000… E por aí vai…

Abraços!

1 curtida
#4 
 long tempoInicial = System.currentTimeMillis();
   .
   .
   .
   .
 long tempoFinal = System.currentTimeMillis();

 System.out.printf("%.3f ms%n", (tempoFinal - tempoInicial) / 1000d);
1 curtida
#5

No java 5 eu recomendo o uso do método nanoTime()
da classe System. Irá lhe dar uma precisão melhor, principalmente para métodos pequenos.

#6

Tem uma classe bacana para isso:

/*
 * This code is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 * A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
 * details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

import java.util.Date;

/**
 * Class for program event timing. Usage:
 * 
 * <pre>
 * Timer timer = new Timer();
 * 
 * // do stuff
 * 
 * System.out.println( timer ); // prints time elapsed since
 * // object was created.
 * 
 * </pre>
 * 
 * @author <a href="mailto:jacob.dreyer@geosoft.no">Jacob Dreyer </a>
 */
public class Timer
{
	private Date start;

	/**
	 * Start timer.
	 */
	public Timer()
	{
		reset();
	}

	/**
	 * Returns exact number of milliseconds since timer was started.
	 * 
	 * @return Number of milliseconds since timer was started.
	 */
	public long getTime()
	{
		Date now = new Date();
		long millis = now.getTime() - start.getTime();

		return millis;
	}

	/**
	 * Restarts the timer.
	 */
	public void reset()
	{
		start = new Date(); // now
	}

	/**
	 * Returns a formatted string showing the elaspsed time suince the instance
	 * was created.
	 * 
	 * @return Formatted time string.
	 */
	public String toString( boolean mili )
	{
		long millis = getTime();

		long hours = millis / 1000 / 60 / 60;
		millis -= hours * 1000 * 60 * 60;

		long minutes = millis / 1000 / 60;
		millis -= minutes * 1000 * 60;

		long seconds = millis / 1000;
		millis -= seconds * 1000;

		StringBuffer time = new StringBuffer();
		if( hours > 0 )
			time.append( hours + ":" );
		if( hours > 0 && minutes < 10 )
			time.append( "0" );
		time.append( minutes + ":" );
		if( seconds < 10 )
			time.append( "0" );
		time.append( seconds );

		if( mili )
		{
			time.append( "." );
			if( millis < 100 )
				time.append( "0" );
			if( millis < 10 )
				time.append( "0" );
			time.append( millis );
		}

		return time.toString();
	}

	@Override
	public String toString()
	{
		return toString( true );
	}

	/**
	 * Testing this class.
	 * 
	 * @param args
	 *            Not used.
	 */
	public static void main( String[] args )
	{
		Timer timer = new Timer();

		for( int i = 0; i < 100000000; i++ )
		{
			double b = 998.43678;
			double c = Math.sqrt( b );
		}

		System.out.println( timer );
	}
}
2 curtidas
#7

Obrigada Feliepe, essa classe é muito útil!!