Is HashMap slow?

[Daniel]

While building business classes, I store the properties/db fields in a
HashMap. So to retrieve the value I use:

String value = (String)fields.get(fieldName);

To save, I pass the HashMap on to a generic Database table class. This
class uses an Iterator to generate the sql statements;

for (Iterator e = fields.keySet().iterator(); e.hasNext() {
..
String key = (String)e.next();
sql += key + " = " + (String)fields.get(key);
..
}


So my question is if the HashMap is too slow for this? If so, is there
a better way to do the same thing?

 

[Matt Humphrey]

While building business classes, I store the properties/db fields in a
HashMap. So to retrieve the value I use:

String value = (String)fields.get(fieldName);

To save, I pass the HashMap on to a generic Database table class. This
class uses an Iterator to generate the sql statements;

for (Iterator e = fields.keySet().iterator(); e.hasNext() {
..
String key = (String)e.next();
sql += key + " = " + (String)fields.get(key);
..
}


So my question is if the HashMap is too slow for this? If so, is there
a better way to do the same thing?

It's very unlikely that HashMap is too slow. If you're concerned about
speed, run a profiler to actually find out where your bottleneck is rather
than trying shotgun optimizations. Using += for String concatenation can
create many short-lived objects, however. The preferred technique is:

StringBuffer sqlBuffer = new StringBuffer (sql);

sqlBuffer.append (key);
sqlBuffer.append ("=");
sqlBufer.append ((String)fields.get(key));


sql = sqlBuffer.toString ();

etc.

Matt Humphrey (e-mail address removed) http://www.iviz.com/

 

[fake_healer]

Thanks for your reply.

It's not slow, but I figured it being better to ask at a state where I
can still change things.

I suspected that the StringBuffer would be a better choice. But since
the strings are so short, I thought it would make much difference.