Accept generic in SparseArray contentEquals

Also updates the JavaDoc.

Bug: 181100924

Test: atest android.util.cts.SparseArrayTest

Change-Id: I3704b2519d10e20d02437037c7f92f5d2ed90dcd

core/api/current.txt

@@ -46300,7 +46300,7 @@ package android.util {
     method public void clear();
     method public android.util.SparseArray<E> clone();
     method public boolean contains(int);
-    method public boolean contentEquals(@Nullable android.util.SparseArray<E>);
+    method public boolean contentEquals(@Nullable android.util.SparseArray<?>);
     method public int contentHashCode();
     method public void delete(int);
     method public E get(int);

core/java/android/util/SparseArray.java

@@ -510,10 +510,12 @@ public class SparseArray<E> implements Cloneable {
     }
 
     /**
+     * Compares the contents of this {@link SparseArray} to the specified {@link SparseArray}.
+     *
      * For backwards compatibility reasons, {@link Object#equals(Object)} cannot be implemented,
      * so this serves as a manually invoked alternative.
      */
-    public boolean contentEquals(@Nullable SparseArray<E> other) {
+    public boolean contentEquals(@Nullable SparseArray<?> other) {
         if (other == null) {
             return false;
         }
@@ -534,6 +536,9 @@ public class SparseArray<E> implements Cloneable {
     }
 
     /**
+     * Returns a hash code value for the contents of this {@link SparseArray}, combining the
+     * {@link Objects#hashCode(Object)} result of all its keys and values.
+     *
      * For backwards compatibility, {@link Object#hashCode()} cannot be implemented, so this serves
      * as a manually invoked alternative.
      */