JavaAntiPatterns

Collection of bad coding practices

Posts Tagged ‘map

Using URLs in Collections

with one comment

java.net.URL objects used as Map keys or Set items can result in a big performance issue. Internal implementation of equals() and hashCode() methods of java.net.URL class performs domain name resolution, so the time of their execution relies on an internet connection speed. If a computer is off-line, the time is nearly equal to a connection timeout (tens of seconds).

The same problem arises every time when URLs equality checking or hash code computation is performed.

Do not use java.net.URL to keep URL values. Use java.net.URI objects or the simple Strings instead.

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Written by Alex

November 22, 2007 at 12:25 pm

Posted in Collections

Tagged with , , , , , ,

Accessing the Map values using keySet iterator

with 13 comments

A common mistake is to retrieve values from a Map while iterating over the Map keys with keySet(). Calling Map.get(key) for each entry is expensive and should be avoided for better performance.

Use entrySet() iterator to avoid the Map.get(key) lookup.

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Written by Alex

November 22, 2007 at 12:02 pm

Posted in Collections

Tagged with , , ,