Fix compilation

pmd-core/src/main/java/net/sourceforge/pmd/util/ConsList.java

@@ -0,0 +1,45 @@
+/*
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.util;
+
+import java.util.AbstractList;
+import java.util.Iterator;
+import java.util.List;
+
+import org.apache.commons.lang3.Validate;
+
+import net.sourceforge.pmd.internal.util.IteratorUtil;
+
+final class ConsList<T> extends AbstractList<T> {
+
+    private final List<? extends T> head;
+    private final List<? extends T> tail;
+    private final int size;
+
+    ConsList(List<? extends T> head, List<? extends T> tail) {
+        this.head = head;
+        this.tail = tail;
+        this.size = head.size() + tail.size();
+    }
+
+    @Override
+    public T get(int index) {
+        Validate.validIndex(this, index);
+        if (index < head.size()) {
+            return head.get(index);
+        }
+        return tail.get(index - head.size());
+    }
+
+    @Override
+    public Iterator<T> iterator() {
+        return IteratorUtil.concat(head.iterator(), tail.iterator());
+    }
+
+    @Override
+    public int size() {
+        return size;
+    }
+}