--- jsr166/src/test/tck/LinkedListTest.java	2016/10/17 00:56:11	1.42
+++ jsr166/src/test/tck/LinkedListTest.java	2018/05/28 21:19:50	1.48
@@ -10,10 +10,11 @@ import java.util.Arrays;
 import java.util.Collection;
 import java.util.Iterator;
 import java.util.LinkedList;
+import java.util.List;
 import java.util.NoSuchElementException;
+import java.util.concurrent.ThreadLocalRandom;
 
 import junit.framework.Test;
-import junit.framework.TestSuite;
 
 public class LinkedListTest extends JSR166TestCase {
     public static void main(String[] args) {
@@ -23,21 +24,33 @@ public class LinkedListTest extends JSR1
     public static Test suite() {
         class Implementation implements CollectionImplementation {
             public Class<?> klazz() { return LinkedList.class; }
-            public Collection emptyCollection() { return new LinkedList(); }
+            public List emptyCollection() { return new LinkedList(); }
             public Object makeElement(int i) { return i; }
             public boolean isConcurrent() { return false; }
             public boolean permitsNulls() { return true; }
         }
-        return newTestSuite(LinkedListTest.class,
-                            CollectionTest.testSuite(new Implementation()));
+        class SubListImplementation extends Implementation {
+            public List emptyCollection() {
+                List list = super.emptyCollection();
+                ThreadLocalRandom rnd = ThreadLocalRandom.current();
+                if (rnd.nextBoolean())
+                    list.add(makeElement(rnd.nextInt()));
+                int i = rnd.nextInt(list.size() + 1);
+                return list.subList(i, i);
+            }
+        }
+        return newTestSuite(
+                LinkedListTest.class,
+                CollectionTest.testSuite(new Implementation()),
+                CollectionTest.testSuite(new SubListImplementation()));
     }
 
     /**
      * Returns a new queue of given size containing consecutive
      * Integers 0 ... n - 1.
      */
-    private LinkedList<Integer> populatedQueue(int n) {
-        LinkedList<Integer> q = new LinkedList<Integer>();
+    private static LinkedList<Integer> populatedQueue(int n) {
+        LinkedList<Integer> q = new LinkedList<>();
         assertTrue(q.isEmpty());
         for (int i = 0; i < n; ++i)
             assertTrue(q.offer(new Integer(i)));
@@ -345,9 +358,11 @@ public class LinkedListTest extends JSR1
      */
     public void testToArray() {
         LinkedList q = populatedQueue(SIZE);
-        Object[] o = q.toArray();
-        for (int i = 0; i < o.length; i++)
-            assertSame(o[i], q.poll());
+        Object[] a = q.toArray();
+        assertSame(Object[].class, a.getClass());
+        for (Object o : a)
+            assertSame(o, q.poll());
+        assertTrue(q.isEmpty());
     }
 
     /**
@@ -358,8 +373,9 @@ public class LinkedListTest extends JSR1
         Integer[] ints = new Integer[SIZE];
         Integer[] array = q.toArray(ints);
         assertSame(ints, array);
-        for (int i = 0; i < ints.length; i++)
-            assertSame(ints[i], q.poll());
+        for (Integer o : ints)
+            assertSame(o, q.poll());
+        assertTrue(q.isEmpty());
     }
 
     /**