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Java autocomplete library.
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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 or transform text;
  • Index data structure for storing the mapping of text to the corresponding sources;
  • Automaton engine for text matching;

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.

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

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