pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / contrib / analyzers / common / src / java / org / apache / lucene / analysis / en / KStemFilter.java

diff --git a/lucene-java-3.5.0/lucene/contrib/analyzers/common/src/java/org/apache/lucene/analysis/en/KStemFilter.java b/lucene-java-3.5.0/lucene/contrib/analyzers/common/src/java/org/apache/lucene/analysis/en/KStemFilter.java
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+package org.apache.lucene.analysis.en;
+
+/**
+ * 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.
+ */
+
+import java.io.IOException;
+
+import org.apache.lucene.analysis.TokenFilter;
+import org.apache.lucene.analysis.TokenStream;
+import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
+import org.apache.lucene.analysis.tokenattributes.KeywordAttribute;
+
+/** A high-performance kstem filter for english.
+ * <p/>
+ * See <a href="http://ciir.cs.umass.edu/pubfiles/ir-35.pdf">
+ * "Viewing Morphology as an Inference Process"</a>
+ * (Krovetz, R., Proceedings of the Sixteenth Annual International ACM SIGIR
+ * Conference on Research and Development in Information Retrieval, 191-203, 1993).
+ * <p/>
+ * All terms must already be lowercased for this filter to work correctly.
+ */
+
+public final class KStemFilter extends TokenFilter {
+  private final KStemmer stemmer = new KStemmer();
+  private final CharTermAttribute termAttribute = addAttribute(CharTermAttribute.class);
+  private final KeywordAttribute keywordAtt = addAttribute(KeywordAttribute.class);
+
+  public KStemFilter(TokenStream in) {
+    super(in);
+  }
+
+  /** Returns the next, stemmed, input Token.
+   *  @return The stemed form of a token.
+   *  @throws IOException
+   */
+  @Override
+  public boolean incrementToken() throws IOException {
+    if (!input.incrementToken())
+      return false;
+
+    char[] term = termAttribute.buffer();
+    int len = termAttribute.length();
+    if ((!keywordAtt.isKeyword()) && stemmer.stem(term, len)) {
+      termAttribute.setEmpty().append(stemmer.asCharSequence());
+    }
+
+    return true;
+  }
+}