1 files changed, 60 insertions, 0 deletions
diff --git a/guava/src/com/google/common/collect/SortedIterables.java b/guava/src/com/google/common/collect/SortedIterables.java
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+++ b/guava/src/com/google/common/collect/SortedIterables.java
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+/*
+ * Copyright (C) 2011 The Guava Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the
+ * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.common.collect;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import com.google.common.annotations.GwtCompatible;
+
+import java.util.Comparator;
+import java.util.SortedSet;
+
+/**
+ * Utilities for dealing with sorted collections of all types.
+ *
+ * @author Louis Wasserman
+ */
+@GwtCompatible
+final class SortedIterables {
+  private SortedIterables() {}
+
+  /**
+   * Returns {@code true} if {@code elements} is a sorted collection using an ordering equivalent
+   * to {@code comparator}.
+   */
+  public static boolean hasSameComparator(Comparator<?> comparator, Iterable<?> elements) {
+    checkNotNull(comparator);
+    checkNotNull(elements);
+    Comparator<?> comparator2;
+    if (elements instanceof SortedSet) {
+      comparator2 = comparator((SortedSet<?>) elements);
+    } else if (elements instanceof SortedIterable) {
+      comparator2 = ((SortedIterable<?>) elements).comparator();
+    } else {
+      return false;
+    }
+    return comparator.equals(comparator2);
+  }
+
+  @SuppressWarnings("unchecked")
+  // if sortedSet.comparator() is null, the set must be naturally ordered
+  public static <E> Comparator<? super E> comparator(SortedSet<E> sortedSet) {
+    Comparator<? super E> result = sortedSet.comparator();
+    if (result == null) {
+      result = (Comparator<? super E>) Ordering.natural();
+    }
+    return result;
+  }
+}