| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package opennlp.tools.util.featuregen; |
| |
| import java.util.List; |
| |
| public class PrefixFeatureGenerator implements AdaptiveFeatureGenerator { |
| |
| static final int DEFAULT_MAX_LENGTH = 4; |
| |
| private final int prefixLength; |
| |
| public PrefixFeatureGenerator() { |
| prefixLength = DEFAULT_MAX_LENGTH; |
| } |
| |
| public PrefixFeatureGenerator(int prefixLength) { |
| this.prefixLength = prefixLength; |
| } |
| |
| @Override |
| public void createFeatures(List<String> features, String[] tokens, int index, |
| String[] previousOutcomes) { |
| String[] prefs = getPrefixes(tokens[index]); |
| for (String pref : prefs) { |
| features.add("pre=" + pref); |
| } |
| } |
| |
| private String[] getPrefixes(String lex) { |
| |
| int prefixes = StrictMath.min(prefixLength, lex.length()); |
| |
| String[] prefs = new String[prefixes]; |
| for (int li = 0; li < prefixes; li++) { |
| prefs[li] = lex.substring(0, StrictMath.min(li + 1, lex.length())); |
| } |
| return prefs; |
| } |
| } |