create priority ordering for instances

scm-core/src/main/java/sonia/scm/Priorities.java

@@ -71,12 +71,25 @@ public final class Priorities
    *
    * @return sorted class list
    */
-  public static <T> List<Class<? extends T>> sort(
-    Iterable<Class<? extends T>> unordered)
+  public static <T> List<Class<? extends T>> sort(Iterable<Class<? extends T>> unordered)
   {
     return new PriorityOrdering<T>().sortedCopy(unordered);
   }
 
+  /**
+   * Returns a list of instances sorted by priority.
+   *
+   * @param <T> type of class
+   * @param unordered unordered instances
+   *
+   * @return sorted instance list
+   */
+  public static <T> List<T> sortInstances(Iterable<T> unordered)
+  {
+    return new PriorityInstanceOrdering<T>().sortedCopy(unordered);
+  }
+
+
   //~--- get methods ----------------------------------------------------------
 
   /**
@@ -125,4 +138,28 @@ public final class Priorities
       return Ints.compare(getPriority(left), getPriority(right));
     }
   }
+
+  /**
+   * {@link Ordering} which orders instances by priority.
+   *
+   * @param <T> type of instance
+   */
+  public static class PriorityInstanceOrdering<T> extends Ordering<T>
+  {
+
+    /**
+     * Compares the left instance with the right instance.
+     *
+     *
+     * @param left left instance
+     * @param right right instance
+     *
+     * @return compare value
+     */
+    @Override
+    public int compare(T left, T right)
+    {
+      return Ints.compare(getPriority(left.getClass()), getPriority(right.getClass()));
+    }
+  }
 }

scm-core/src/test/java/sonia/scm/PrioritiesTest.java

@@ -98,6 +98,21 @@ public class PrioritiesTest
     assertThat(cls, contains(B.class, C.class, A.class, D.class));
   }
 
+  @Test
+  @SuppressWarnings("unchecked")
+  public void shouldSortInstances()
+  {
+    A a = new A();
+    B b = new B();
+    C c = new C();
+    D d = new D();
+
+    List<?> instances = ImmutableList.of(a, b, c, d);
+
+    instances = Priorities.sortInstances(instances);
+    assertThat(instances, contains(b, c, a, d));
+  }
+
   //~--- inner classes --------------------------------------------------------
 
   /**