Benchmark for Java string operations
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Java string operations benchmark

This small project is a simple benchmark for simple string-oriented algorithms in order to find a most optimal solution, given execution in a Java Virtual Machine.

The problem

The problem is stripping all the control characters in a given string

  • that is, removing these characters, replacing then with nothing.

Definition of "control character" is vague, but for most purposes, it would be acceptable to assume that characters with ASCII/Unicode codes [0..31] are control characters and all others are not.

Structure of project

Benchmark consists of running several algorithms repeatedly. Basically, everything that's going to be tested is just hardcoded in main() method of There are 3 basic types of modules needed for testing:

  • String sources - modules that somehow get the strings ready and supply them as needed. Need to implement interface StringSource which defines only one simple method: String nextString(). Using various string sources dramatically affects which strings are processed, thus affects optimization routes JVM takes and ultimately affects performance. Examples for these modules include passing the same constant string over and over, generation of random strings with given properties, reading strings from a local file or receiving them from a network connection.

  • Processing algorithms - modules that implement processing algorithms itself. These classes must implement StripAlgorithm and thus define a single method String strip(String).

  • String destinations - modules that consume strings after being processed by algorithm. If there would be no consumers for strings, JVM could ultimately optimize the whole processing thing out, so no processing would happen at all and algorithm would "work" instantly. Simplest form of string destination is SimpleCount which does simplest and fastest non-trivial string content analysis operation which won't be optimized out. More complex examples could include writing a string to local file or sending it over the network.

Running the benchmark

Given this structure, basically, testing consists of:

  • Create one or more of objects to test (StringSource, StripAlgorithm, StringDestination), for example:

      StringSource src = new SingleString();
      StringDestination dst = new SimpleCount();
      StripAlgorithm alg[] = new StripAlgorithm[] {
              new StringReplaceAll(),
              new MatcherReplace(),
              new StringBuilderCodePoint(),
  • Run tests for algorithms' correctness (checks that all outputs for all algorithms match):

      assureCorrectness(10000, src, alg);
  • Run tests to measure algorithms' speed:

      benchmarkSpeed(1000000, src, dst, alg);

Sample testing procedure that test almost all algorithms is included in default main() implementation.