TreeSet/TreeMap should implement Cloneable and offer clone() (#10146)

Fixes #10145

Author: niloc132

user/super/com/google/gwt/emul/java/util/TreeMap.java

@@ -28,7 +28,7 @@
  * @param <K> key type
  * @param <V> value type
  */
-public class TreeMap<K, V> extends AbstractNavigableMap<K, V> implements Serializable {
+public class TreeMap<K, V> extends AbstractNavigableMap<K, V> implements Serializable, Cloneable {
   /*
    * Implementation derived from public domain C implementation as of 5
    * September 2007 at:
@@ -502,6 +502,10 @@ public void clear() {
     size = 0;
   }
 
+  public Object clone() {
+    return new TreeMap<K, V>(this);
+  }
+
   @Override
   public Comparator<? super K> comparator() {
     return Comparators.naturalOrderToNull(cmp);

user/super/com/google/gwt/emul/java/util/TreeSet.java

@@ -26,7 +26,8 @@
  *
  * @param <E> element type.
  */
-public class TreeSet<E> extends AbstractSet<E> implements NavigableSet<E>, Serializable {
+public class TreeSet<E> extends AbstractSet<E> implements NavigableSet<E>, Serializable,
+    Cloneable {
 
   /**
    * TreeSet is stored as a TreeMap of the requested type to a constant Boolean.
@@ -77,6 +78,10 @@ public void clear() {
     map.clear();
   }
 
+  public Object clone() {
+    return new TreeSet(new TreeMap<E, Boolean>(map));
+  }
+
   @Override
   public Comparator<? super E> comparator() {
     return map.comparator();

user/test/com/google/gwt/emultest/java/util/TreeMapTest.java

@@ -281,21 +281,28 @@ public void testClear_throwsUnsupportedOperationException() {
 
   /** Test method for 'java.lang.Object.clone()'. */
   public void testClone() {
-    // Map<K, V> map = createMap();
+    TreeMap<K, V> map = createTreeMap();
     // Check empty clone behavior
-    // TODO (rlo) having .clone() in the code kills the test
-    // SortedMap<K, V> clone = (SortedMap<K, V>)
-    // map.clone();
-    // assertNotNull(clone);
-    // testEquivalent(map, clone);
-    //
-    // // Check non-empty clone behavior
-    // map.put(KEY_1, getValues()[0]);
-    // map.put(KEY_2, getValues()[1]);
-    // map.put(KEY_3, getValues()[2]);
-    // clone = (SortedMap<K, V>) map.clone();
-    // assertNotNull(clone);
-    // testEquivalent(map, clone);
+    SortedMap<K, V> clone = (SortedMap<K, V>) map.clone();
+    assertNotNull(clone);
+    _assertEquals(map, clone);
+    assertSame(map.comparator(), clone.comparator());
+
+    // Check non-empty clone behavior
+    K[] keys = getKeys();
+    V[] values = getValues();
+    map.put(keys[0], values[0]);
+    map.put(keys[1], values[1]);
+    map.put(keys[2], values[2]);
+
+    // Ensure no shared state between original and clone
+    assertFalse(map.equals(clone));
+
+    // Clone the non-empty map
+    clone = (SortedMap<K, V>) map.clone();
+    assertNotNull(clone);
+    _assertEquals(map, clone);
+    assertSame(map.comparator(), clone.comparator());
   }
 
   /**

user/test/com/google/gwt/emultest/java/util/TreeSetTest.java

@@ -682,6 +682,18 @@ public void testEquals() {
     assertFalse(set0.equals(set1));
   }
 
+  public void testSetClone() {
+    TreeSet<E> set = createTreeSet();
+    TreeSet<E> clone = (TreeSet<E>) set.clone();
+    assertEquals(set, clone);
+
+    set.add(getKeys()[0]);
+    assertFalse(set.equals(clone));
+
+    clone = (TreeSet<E>) set.clone();
+    assertEquals(set, clone);
+  }
+
   /**
    * Test method for 'java.util.SortedSet.first()'.
    *