1 files changed, 81 insertions, 0 deletions
diff --git a/guava/src/com/google/common/collect/NullsFirstOrdering.java b/guava/src/com/google/common/collect/NullsFirstOrdering.java
new file mode 100644
index 0000000..2e8a3ac
--- /dev/null
+++ b/guava/src/com/google/common/collect/NullsFirstOrdering.java
@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2007 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 com.google.common.annotations.GwtCompatible;
+
+import java.io.Serializable;
+
+import javax.annotation.Nullable;
+
+/** An ordering that treats {@code null} as less than all other values. */
+@GwtCompatible(serializable = true)
+final class NullsFirstOrdering<T> extends Ordering<T> implements Serializable {
+  final Ordering<? super T> ordering;
+
+  NullsFirstOrdering(Ordering<? super T> ordering) {
+    this.ordering = ordering;
+  }
+
+  @Override public int compare(@Nullable T left, @Nullable T right) {
+    if (left == right) {
+      return 0;
+    }
+    if (left == null) {
+      return RIGHT_IS_GREATER;
+    }
+    if (right == null) {
+      return LEFT_IS_GREATER;
+    }
+    return ordering.compare(left, right);
+  }
+
+  @Override public <S extends T> Ordering<S> reverse() {
+    // ordering.reverse() might be optimized, so let it do its thing
+    return ordering.reverse().nullsLast();
+  }
+
+  @SuppressWarnings("unchecked") // still need the right way to explain this
+  @Override public <S extends T> Ordering<S> nullsFirst() {
+    return (Ordering<S>) this;
+  }
+
+  @Override public <S extends T> Ordering<S> nullsLast() {
+    return ordering.nullsLast();
+  }
+
+  @Override public boolean equals(@Nullable Object object) {
+    if (object == this) {
+      return true;
+    }
+    if (object instanceof NullsFirstOrdering) {
+      NullsFirstOrdering<?> that = (NullsFirstOrdering<?>) object;
+      return this.ordering.equals(that.ordering);
+    }
+    return false;
+  }
+
+  @Override public int hashCode() {
+    return ordering.hashCode() ^ 957692532; // meaningless
+  }
+
+  @Override public String toString() {
+    return ordering + ".nullsFirst()";
+  }
+
+  private static final long serialVersionUID = 0;
+}