Similar to my earlier post ‘ Measuring “String.indexOfAny(String)” performance’, I added a new JMH test class - StringConcatenation - on repository. Given this, it is reasonable to suspect that String.format() may have some overhead for our simple concatenation use case.īut does it? (did JDK folks pull another impressive feat here? :) ) And if so, how much? So Let’s Ask Our Friend JMH To Have a Look Similarly it may be necessary to build secondary data structures for handling details of formatting, at least or some cases - and even if not for our case, the support and design has to allow for that. And unlike with something like pile() for regular expressions, there is no way to pre-process that. The important part to note is that decoding of the format String to use is overhead that either occurs for each call, or, JDK has to use some elaborate caching for it. We just happen use this power tool for a low-power use case. One thing to note, however, is that while usage here is for the same task, underlying implementation of String.format() is essentially much, much more complicated - it is a quite powerful tool for all types of String formatting. But Should String.format() Have Low Overhead? append('.').append(tableName).toString() Īnd one might expect these approaches to perform similarly, given that from the user perspective they perform the same task. This is functionally equivalent to: String key = keyspace + "." + tableName // or key = new StringBuilder().append(keyspace). For example: String key = String.format("%s.%s", keyspace, tableName) The specific case that caught my eye - and that represents a wider class of similar use cases - is that of String concatenation for creating Strings like compound keys.
![java string formatter java string formatter](https://i.ytimg.com/vi/priVwrgfd7w/maxresdefault.jpg)
This is post about one such case: the surprisingly poor performance of String.format() for simple String concatenation More Specifically…
#JAVA STRING FORMATTER CODE#
Knowing these outliers can be useful when dealing with performance-sensitive code (like tight loops for something called thousands of times per second or more etc.).
![java string formatter java string formatter](https://linuxhint.com/wp-content/uploads/2020/08/1-6.jpg)
![java string formatter java string formatter](https://i.ytimg.com/vi/LUv9OBVlFc4/maxresdefault.jpg)
So as general guideline I tend to trust that if the JDK has a method for doing something in a simple way it is perfectly fine for most use and likely performs well enough.īut I have also found that occasionally some specific classes or methods may perform surprisingly poorly. In the past I have found that the functionality in the JDK is usually well optimized, and performs reasonably well for the task, considering general nature and applicability of the functionality offered. Aka “Why is String.format() SO slow?” Background