core/src/main/java/com/orientechnologies/orient/core/index/OIndexes.java
public static Set<String> getIndexEngines() {
    final Set<String> engines = new HashSet<>();
    final Iterator<OIndexFactory> ite = getAllFactories();
    while (ite.hasNext()) {
      engines.addAll(ite.next().getAlgorithms());
    }
    return engines;
  }
public static Set<String> getIndexEngines() {
    final Set<String> engines = new HashSet<>();
    final Iterator<OIndexFactory> ite = getAllFactories();
    while (ite.hasNext()) {
      engines.addAll(ite.next().getAlgorithms());
    }
    return engines;
  }
public static Set < String > getIndexEngines ( ) { final Set < String > engines = new HashSet <> ( ) ; final Iterator < OIndexFactory > ite = getAllFactories ( ) ; while ( ite . hasNext ( ) ) { engines . addAll ( ite . next ( ) . getAlgorithms ( ) ) ; } return engines ; }
Iterates on all factories and append all index engines.

@return Set of all index engines.
Iterates on all factories and append all index engines .