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Completely is a Java autocomplete library.

Autocomplete involves predicting a word or phrase that the user may type based on a partial query. The goal is to provide instant feedback and avoid unnecessary typing as the user formulates queries. Performance is a key issue since each keystroke from the user could invoke a query, and each query should be answered within a few milliseconds. What's more, because users often make spelling mistakes while typing, autocomplete should tolerate errors and differences in representation.

Needless to say, a standard sequential search is bound to be ineffective for anything other than small data sets. By contrast, Completely relies on text preprocessing to create an in-memory index for efficiently answering searches in large data sets. All in all, there are three fundamental components at play:

  • Analyzer function to filter, tokenize and/or transform text prior to indexing;
  • Index data structure for storing the mapping of text to the corresponding sources;
  • Automaton engine for text matching when searching;

Together these can used to tackle a variety of use cases, wherein the choice of components or combination thereof depends solely on the application at hand.


All release artifacts are available for download from the Maven central repository.

Build from source

Building Completely requires Maven 3 and Java 8, or newer.

Download the source code:

git clone

Build the JAR package:

mvn clean package -DskipTests

Run the sample

Install artifacts to the local repository:

mvn install

Execute the main class:

mvn exec:java -pl sample


  • Bořivoj Melichar. Approximate String Matching by Finite Automata;
  • Gonzalo Navarro. A Guided Tour to Approximate String Matching;
  • Leonid Boytsov. Indexing Methods for Approximate Dictionary Searching: Comparative Analysis;
  • Marios Hadjieleftheriou and Divesh Srivastava. Approximate String Processing;
  • Surajit Chaudhuri and Raghav Kaushik. Extending Autocompletion To Tolerate Errors;


Released under The Apache Software License, Version 2.0