Re: How to tune up this little piece of code?

From:

www <www@nospam.com>

Newsgroups:

comp.lang.java.programmer

Date:

Tue, 16 Jan 2007 13:01:38 -0500

Message-ID:

<eoj3u3$34i$1@news.nems.noaa.gov>

www wrote:

Hi,

I am using Eclipse profiler and have found that the following method,
getDate(), in a utility class was called more than 3000 times and cost 5
seconds of accumulative time.

public class Helper //a utility class
{
    ...//other helping methods

    //get the String and return an object of Date
    public static Date getDate(String str)
    {
        Date aDate = null;
        if (timeString != null)
        {
            SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd
HH:mm:ss");
            format.setTimeZone(TimeZone.getTimeZone("UTC"));
            try
            {
                aDate = format.parse(str);
            }
            catch ... //omitted
        }

        return aDate;
    }
}

I am not very good with code performance. I feel at least something
below should be better:

public class Helper
{
    ...//other helping methods

    private static Date aDate = null;
    private static SimpleDateFormat format = (new
SimpleDateFormat("yyyy-MM-dd
HH:mm:ss")).setTimeZone(TimeZone.getTimeZone("UTC"));
    public static Date getDate(String str) //now the method is much
shorter
    {
        if (timeString != null)
        {
            try
            {
                aDate = format.parse(str);
            }
            catch ... //omitted
        }

        return aDate;
    }

}

Do you think my new code is legal? Is better?

I just tested the following code. It became worse. It costs 6.3 seconds
now. I am not clear why and why it didn't get better. Thank you very much.

public class Helper
{
     ...//other helping methods

     private static Date aDate = null;
     private static SimpleDateFormat format = new
SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
     public static Date getDate(String str) //now the method is much
shorter
     {
         if (timeString != null)
         {
             try
             {
        format.setTimeZone(TimeZone.getTimeZone("UTC"))
                 aDate = format.parse(str);
             }
             catch ... //omitted
         }

         return aDate;
     }

}