Use ArrayList instead of LinkedList

The paragraph neighbor processing is based entirely on List.get(),
making a LinkedList a very inefficient choice.

dkpro-c4corpus-boilerplate/src/main/java/de/tudarmstadt/ukp/dkpro/c4corpus/boilerplate/impl/JusTextBoilerplateRemoval.java

@@ -32,11 +32,11 @@
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.io.StringWriter;
+import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
-import java.util.LinkedList;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
@@ -113,7 +113,7 @@ private Document convertHtmlToDoc(String html)
      * Initialize the Paragraph explorer class in order to convert a document to
      * a list of blocks (paragraphs)
      */
-    private LinkedList<Paragraph> makeParagraphs(Node node)
+    private ArrayList<Paragraph> makeParagraphs(Node node)
     {
         ParagraphsExplorer pe = new ParagraphsExplorer();
         node.traverse(pe); //begin the traversal of the doc
@@ -274,12 +274,11 @@ private PARAGRAPH_TYPE getNextNeighbourOptimized(int i, List<Paragraph> paragrap
      * <li>postprocessing of header blocks
      * </ol>
      * 
-     * FIXME: This can behave pathologically in the presence of large lists of "paragraphs"
-     * with no textual content. In this case the maxHeadingDistance parameter isn't adequate
-     * to short circuit large amounts of processing. We may need to max number of elements
-     * to search (10? 20?).
+     * NOTE: Normally we'd use List<Paragraph> in the definition, but this method makes extensive
+     * use of List.get() which is very inefficient with other list implementations such as LinkedList.
+     * This could be rewritten to use ListIterators to generalize it, but I don't see the point.
      */
-    private void reclassifyContextSensitive(List<Paragraph> paragraphs, int maxHeadingDistance)
+    private void reclassifyContextSensitive(ArrayList<Paragraph> paragraphs, int maxHeadingDistance)
     {
         // Default classification is the same as the context-free classification
         for (Paragraph p : paragraphs) {
@@ -408,7 +407,7 @@ private List<Paragraph> classify(String htmlText, Set<String> stopwordsSet, int
         }
 
         Document jSoupDoc = convertHtmlToDoc(htmlText);
-        LinkedList<Paragraph> paragraphs = makeParagraphs(jSoupDoc);
+        ArrayList<Paragraph> paragraphs = makeParagraphs(jSoupDoc);
         //context-free classification
         classifyContextFree(paragraphs, stopwordsSet, lengthLow, lengthHigh,
                 stopwordsLow, stopwordsHigh, maxLinkDensity);

dkpro-c4corpus-boilerplate/src/main/java/de/tudarmstadt/ukp/dkpro/c4corpus/boilerplate/impl/ParagraphsExplorer.java

@@ -23,10 +23,10 @@
 import org.jsoup.nodes.TextNode;
 import org.jsoup.select.NodeVisitor;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashSet;
-import java.util.LinkedList;
 import java.util.Set;
 import java.util.regex.Pattern;
 
@@ -48,7 +48,7 @@ public class ParagraphsExplorer
             new HashSet<String>(Arrays.asList(new String[] { "blockquote", "caption", "center", "col", "colgroup", "dd",
                     "div", "dl", "dt", "fieldset", "form", "legend", "optgroup", "option", "p", "pre", "table", "td",
                     "textarea", "tfoot", "th", "thead", "tr", "ul", "li", "h1", "h2", "h3", "h4", "h5", "h6" })));
-    private final LinkedList<Paragraph> paragraphs;
+    private final ArrayList<Paragraph> paragraphs;
     private Paragraph currentParagraph = null;
     private boolean lastBR = false;
     private boolean inHeading = false;
@@ -62,7 +62,7 @@ public enum AncestorState
 
     public ParagraphsExplorer()
     {
-        this.paragraphs = new LinkedList<>();
+        this.paragraphs = new ArrayList<>();
     }
 
     @Override
@@ -106,7 +106,7 @@ public void tail(Node node, int depth)
      *
      * @return paragraphs
      */
-    public LinkedList<Paragraph> getParagraphs()
+    public ArrayList<Paragraph> getParagraphs()
     {
         return paragraphs;
     }