Simplify creation of lists returned by generated Parser new methods

This also avoids allocating a full ArrayList if just one node is pushed
(which is by far the most common case).

src/main/java/org/sablecc/sablecc/GenerateAlternativeCodeForParser.java

@@ -130,20 +130,32 @@ public class GenerateAlternativeCodeForParser extends DepthFirstAdapter
   {
     try
     {
-      PTerm firstTerm = null;
-      for(PTerm term : node.getTerms())
-      {
-        if(firstTerm == null)
+      if(node.getTerms().isEmpty())
       {
-          firstTerm = term;
+        macros.apply(file, "ParserNewTailEmpty", null);
       }
-        macros.apply(file, "ParserNewBodyListAdd", new String[] {getVariableName(term)});
-      }
-      if (firstTerm != null && popCount > 0) {
+      else
+      {
+        PTerm firstTerm = node.getTerms().get(0);
+        if (popCount > 0) {
           // The nodeArrayList variables are numbered starting at 1, so the first popped variable has the number popCount and not popCount-1.
           macros.apply(file, "ParserNewCheck", new String[] {getVariableName(firstTerm), String.valueOf(popCount)});
         }
-      macros.apply(file, "ParserNewTail");
+
+        if(node.getTerms().size() == 1)
+        {
+          macros.apply(file, "ParserNewTailSingle", new String[] {getVariableName(firstTerm)});
+        }
+        else
+        {
+          macros.apply(file, "ParserNewTailMultiHead");
+          for(PTerm term : node.getTerms())
+          {
+            macros.apply(file, "ParserNewTailMultiElement", new String[] {getVariableName(term)});
+          }
+          macros.apply(file, "ParserNewTailMultiTail");
+        }
+      }
     }
     catch(IOException e)
     {

src/main/resources/org/sablecc/sablecc/parser.txt

@@ -15,6 +15,7 @@ import java.io.BufferedInputStream;
 import java.io.InputStream;
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.LinkedList;
 import java.util.List;
@@ -314,8 +315,6 @@ Macro:ParserNewHeader
 
     private List<Object> new$0$() /* reduce $1$ */
     {
-        List<Object> nodeList = new ArrayList<>();
-
 
 $
 
@@ -390,18 +389,35 @@ Macro:ParserTypedLinkedListAddAll
 
 $
 
-Macro:ParserNewBodyListAdd
-        nodeList.add($0$);
+Macro:ParserNewCheck
+        checkResult($0$, nodeArrayList1, nodeArrayList$1$);
 
 $
 
-Macro:ParserNewCheck
-        checkResult($0$, nodeArrayList1, nodeArrayList$1$);
+Macro:ParserNewTailEmpty
+        return Collections.emptyList();
+    }
+
+$
+
+Macro:ParserNewTailSingle
+        return Collections.<Object>singletonList($0$);
+    }
+
+$
+
+Macro:ParserNewTailMultiHead
+        return Arrays.asList(new Object[] {
+
+$
+
+Macro:ParserNewTailMultiElement
+            $0$,
 
 $
 
-Macro:ParserNewTail
-        return nodeList;
+Macro:ParserNewTailMultiTail
+        });
     }
 
 $