Extract ordering functions to MammothLists

1 files changed, 9 insertions, 0 deletions

diff --git a/src/main/java/org/zwobble/mammoth/util/MammothLists.java b/src/main/java/org/zwobble/mammoth/util/MammothLists.java
index 59f23f8..d6d1136 100644
--- a/src/main/java/org/zwobble/mammoth/util/MammothLists.java
+++ b/src/main/java/org/zwobble/mammoth/util/MammothLists.java
@@ -3,6 +3,7 @@ package org.zwobble.mammoth.util;
 import com.google.common.base.Function;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
+import com.google.common.collect.Ordering;
 
 import java.util.List;
 
@@ -22,4 +23,12 @@ public class MammothLists {
     public static <T, R> List<R> eagerFlatMap(Iterable<T> iterable, Function<T, Iterable<R>> function) {
         return ImmutableList.copyOf(Iterables.concat(Iterables.transform(iterable, function)));
     }
+
+    public static <T, R extends Comparable<R>> List<T> orderedBy(Iterable<T> iterable, Function<T, R> getKey) {
+        return orderBy(getKey).sortedCopy(iterable);
+    }
+
+    private static <T, R extends Comparable<R>> Ordering<T> orderBy(Function<T, R> getKey) {
+        return Ordering.from((first, second) -> getKey.apply(first).compareTo(getKey.apply(second)));
+    }
 }