public void freeze() {
        if (proximityTable.length!=proximityLimit*2+1)
            throw new IllegalStateException("Proximity table length is " + proximityTable.length + ". Must be " +
                                            (proximityLimit*2+1) +
                                            " (proximityLimit*2+1), because the proximity limit is " + proximityLimit);
        frozen=true;
    }
Freezes this object. All changes after this point will cause an IllegalStateException.
This must be frozen before being handed to a calculator.

@throws IllegalStateException if this parameter object is inconsistent. In this case, this is not frozen.
searchlib/src/main/java/com/yahoo/searchlib/ranking/features/fieldmatch/FieldMatchMetricsParameters.java