j2k: flatten test cases and testData directory structure

Move j2k/test/tests -> j2k/tests, j2k/test/testData -> j2k/testData

j2k/testData/fileOrElement/list/Lists.java

@@ -0,0 +1,15 @@
+//file
+import java.util.*;
+
+public class Lists {
+    public void test() {
+        List<Object> xs = new ArrayList<Object>();
+        List<Object> ys = new LinkedList<Object>();
+        ArrayList<Object> zs = new ArrayList<Object>();
+        xs.add(null);
+        ys.add(null);
+        xs.clear();
+        ys.clear();
+        zs.add(null);
+    }
+}