--- a/jdk/src/share/classes/java/util/Comparators.java	Fri Apr 12 12:12:53 2013 -0700
+++ b/jdk/src/share/classes/java/util/Comparators.java	Fri Apr 12 12:41:18 2013 -0700
@@ -261,6 +261,7 @@
      * according to the supplied {@code Comparator}
      */
     public static<T> BinaryOperator<T> lesserOf(Comparator<? super T> comparator) {
+        Objects.requireNonNull(comparator);
         return (a, b) -> comparator.compare(a, b) <= 0 ? a : b;
     }
 
@@ -274,6 +275,7 @@
      * according to the supplied {@code Comparator}
      */
     public static<T> BinaryOperator<T> greaterOf(Comparator<? super T> comparator) {
+        Objects.requireNonNull(comparator);
         return (a, b) -> comparator.compare(a, b) >= 0 ? a : b;
     }
 }

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/test/java/util/Comparators/BasicTest.java	Fri Apr 12 12:41:18 2013 -0700
@@ -0,0 +1,412 @@
+/*
+ * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8001667 8010279
+ * @run testng BasicTest
+ */
+
+import java.util.Comparator;
+import java.util.Comparators;
+import java.util.AbstractMap;
+import java.util.Map;
+import org.testng.annotations.Test;
+
+import java.util.function.BinaryOperator;
+import java.util.function.Function;
+import java.util.function.ToIntFunction;
+import java.util.function.ToLongFunction;
+import java.util.function.ToDoubleFunction;
+
+import static org.testng.Assert.assertEquals;
+import static org.testng.Assert.assertTrue;
+import static org.testng.Assert.assertSame;
+import static org.testng.Assert.fail;
+
+/**
+ * Unit tests for helper methods in Comparators
+ */
+@Test(groups = "unit")
+public class BasicTest {
+    private static class Thing {
+        public final int intField;
+        public final long longField;
+        public final double doubleField;
+        public final String stringField;
+
+        private Thing(int intField, long longField, double doubleField, String stringField) {
+            this.intField = intField;
+            this.longField = longField;
+            this.doubleField = doubleField;
+            this.stringField = stringField;
+        }
+
+        public int getIntField() {
+            return intField;
+        }
+
+        public long getLongField() {
+            return longField;
+        }
+
+        public double getDoubleField() {
+            return doubleField;
+        }
+
+        public String getStringField() {
+            return stringField;
+        }
+    }
+
+    private final int[] intValues = { -2, -2, -1, -1, 0, 0, 1, 1, 2, 2 };
+    private final long[] longValues = { -2, -2, -1, -1, 0, 0, 1, 1, 2, 2 };
+    private final double[] doubleValues = { -2, -2, -1, -1, 0, 0, 1, 1, 2, 2 };
+    private final String[] stringValues = { "a", "a", "b", "b", "c", "c", "d", "d", "e", "e" };
+    private final int[] comparisons = { 0, -1, 0, -1, 0, -1, 0, -1, 0 };
+
+    private<T> void assertComparisons(T[] things, Comparator<T> comp, int[] comparisons) {
+        for (int i=0; i<comparisons.length; i++) {
+            assertEquals(comparisons.length + 1, things.length);
+            assertEquals(comparisons[i], comp.compare(things[i], things[i+1]));
+            assertEquals(-comparisons[i], comp.compare(things[i+1], things[i]));
+        }
+    }
+
+    public void testIntComparator() {
+        Thing[] things = new Thing[intValues.length];
+        for (int i=0; i<intValues.length; i++)
+            things[i] = new Thing(intValues[i], 0L, 0.0, null);
+        Comparator<Thing> comp = Comparators.comparing(new ToIntFunction<BasicTest.Thing>() {
+            @Override
+            public int applyAsInt(Thing thing) {
+                return thing.getIntField();
+            }
+        });
+
+        assertComparisons(things, comp, comparisons);
+    }
+
+    public void testLongComparator() {
+        Thing[] things = new Thing[longValues.length];
+        for (int i=0; i<longValues.length; i++)
+            things[i] = new Thing(0, longValues[i], 0.0, null);
+        Comparator<Thing> comp = Comparators.comparing(new ToLongFunction<BasicTest.Thing>() {
+            @Override
+            public long applyAsLong(Thing thing) {
+                return thing.getLongField();
+            }
+        });
+
+        assertComparisons(things, comp, comparisons);
+    }
+
+    public void testDoubleComparator() {
+        Thing[] things = new Thing[doubleValues.length];
+        for (int i=0; i<doubleValues.length; i++)
+            things[i] = new Thing(0, 0L, doubleValues[i], null);
+        Comparator<Thing> comp = Comparators.comparing(new ToDoubleFunction<BasicTest.Thing>() {
+            @Override
+            public double applyAsDouble(Thing thing) {
+                return thing.getDoubleField();
+            }
+        });
+
+        assertComparisons(things, comp, comparisons);
+    }
+
+    public void testComparing() {
+        Thing[] things = new Thing[doubleValues.length];
+        for (int i=0; i<doubleValues.length; i++)
+            things[i] = new Thing(0, 0L, 0.0, stringValues[i]);
+        Comparator<Thing> comp = Comparators.comparing(new Function<Thing, String>() {
+            @Override
+            public String apply(Thing thing) {
+                return thing.getStringField();
+            }
+        });
+
+        assertComparisons(things, comp, comparisons);
+    }
+
+    public void testNaturalOrderComparator() {
+        Comparator<String> comp = Comparators.naturalOrder();
+
+        assertComparisons(stringValues, comp, comparisons);
+    }
+
+    public void testReverseComparator() {
+        Comparator<String> cmpr = Comparators.reverseOrder();
+        Comparator<String> cmp = cmpr.reverseOrder();
+
+        assertEquals(cmp.reverseOrder(), cmpr);
+        assertEquals(0, cmp.compare("a", "a"));
+        assertEquals(0, cmpr.compare("a", "a"));
+        assertTrue(cmp.compare("a", "b") < 0);
+        assertTrue(cmpr.compare("a", "b") > 0);
+        assertTrue(cmp.compare("b", "a") > 0);
+        assertTrue(cmpr.compare("b", "a") < 0);
+    }
+
+    public void testReverseComparator2() {
+        Comparator<String> cmp = (s1, s2) -> s1.length() - s2.length();
+        Comparator<String> cmpr = cmp.reverseOrder();
+
+        assertEquals(cmpr.reverseOrder(), cmp);
+        assertEquals(0, cmp.compare("abc", "def"));
+        assertEquals(0, cmpr.compare("abc", "def"));
+        assertTrue(cmp.compare("abcd", "def") > 0);
+        assertTrue(cmpr.compare("abcd", "def") < 0);
+        assertTrue(cmp.compare("abc", "defg") < 0);
+        assertTrue(cmpr.compare("abc", "defg") > 0);
+    }
+
+    @Test(expectedExceptions=NullPointerException.class)
+    public void testReverseComparatorNPE() {
+        Comparator<String> cmp = Comparators.reverseOrder(null);
+    }
+
+    public void testComposeComparator() {
+        // Longer string in front
+        Comparator<String> first = (s1, s2) -> s2.length() - s1.length();
+        Comparator<String> second = Comparators.naturalOrder();
+        Comparator<String> composed = Comparators.compose(first, second);
+
+        assertTrue(composed.compare("abcdefg", "abcdef") < 0);
+        assertTrue(composed.compare("abcdef", "abcdefg") > 0);
+        assertTrue(composed.compare("abcdef", "abcdef") == 0);
+        assertTrue(composed.compare("abcdef", "ghijkl") < 0);
+        assertTrue(composed.compare("ghijkl", "abcdefg") > 0);
+    }
+
+    private <K, V> void assertPairComparison(K k1, V v1, K k2, V v2,
+                                        Comparator<Map.Entry<K, V>> ck,
+                                        Comparator<Map.Entry<K, V>> cv) {
+        final Map.Entry<K, V> p11 = new AbstractMap.SimpleImmutableEntry<>(k1, v1);
+        final Map.Entry<K, V> p12 = new AbstractMap.SimpleImmutableEntry<>(k1, v2);
+        final Map.Entry<K, V> p21 = new AbstractMap.SimpleImmutableEntry<>(k2, v1);
+        final Map.Entry<K, V> p22 = new AbstractMap.SimpleImmutableEntry<>(k2, v2);
+
+        assertTrue(ck.compare(p11, p11) == 0);
+        assertTrue(ck.compare(p12, p11) == 0);
+        assertTrue(ck.compare(p11, p12) == 0);
+        assertTrue(ck.compare(p12, p22) < 0);
+        assertTrue(ck.compare(p12, p21) < 0);
+        assertTrue(ck.compare(p21, p11) > 0);
+        assertTrue(ck.compare(p21, p12) > 0);
+
+        assertTrue(cv.compare(p11, p11) == 0);
+        assertTrue(cv.compare(p12, p11) > 0);
+        assertTrue(cv.compare(p11, p12) < 0);
+        assertTrue(cv.compare(p12, p22) == 0);
+        assertTrue(cv.compare(p12, p21) > 0);
+        assertTrue(cv.compare(p21, p11) == 0);
+        assertTrue(cv.compare(p21, p12) < 0);
+
+        Comparator<Map.Entry<K, V>> cmp = Comparators.compose(ck, cv);
+        assertTrue(cmp.compare(p11, p11) == 0);
+        assertTrue(cmp.compare(p12, p11) > 0);
+        assertTrue(cmp.compare(p11, p12) < 0);
+        assertTrue(cmp.compare(p12, p22) < 0);
+        assertTrue(cmp.compare(p12, p21) < 0);
+        assertTrue(cmp.compare(p21, p11) > 0);
+        assertTrue(cmp.compare(p21, p12) > 0);
+
+        cmp = Comparators.compose(cv, ck);
+        assertTrue(cmp.compare(p11, p11) == 0);
+        assertTrue(cmp.compare(p12, p11) > 0);
+        assertTrue(cmp.compare(p11, p12) < 0);
+        assertTrue(cmp.compare(p12, p22) < 0);
+        assertTrue(cmp.compare(p12, p21) > 0);
+        assertTrue(cmp.compare(p21, p11) > 0);
+        assertTrue(cmp.compare(p21, p12) < 0);
+    }
+
+    public void testKVComparatorable() {
+        assertPairComparison(1, "ABC", 2, "XYZ",
+                         Comparators.<Integer, String>naturalOrderKeys(),
+                         Comparators.<Integer, String>naturalOrderValues());
+    }
+
+    private static class People {
+        final String firstName;
+        final String lastName;
+        final int age;
+
+        People(String first, String last, int age) {
+            firstName = first;
+            lastName = last;
+            this.age = age;
+        }
+
+        String getFirstName() { return firstName; }
+        String getLastName() { return lastName; }
+        int getAge() { return age; }
+        long getAgeAsLong() { return (long) age; };
+        double getAgeAsDouble() { return (double) age; };
+    }
+
+    private final People people[] = {
+        new People("John", "Doe", 34),
+        new People("Mary", "Doe", 30),
+        new People("Maria", "Doe", 14),
+        new People("Jonah", "Doe", 10),
+        new People("John", "Cook", 54),
+        new People("Mary", "Cook", 50),
+    };
+
+    public void testKVComparators() {
+        // Comparator<People> cmp = Comparators.naturalOrder(); // Should fail to compiler as People is not comparable
+        // We can use simple comparator, but those have been tested above.
+        // Thus choose to do compose for some level of interation.
+        Comparator<People> cmp1 = Comparators.comparing((Function<People, String>) People::getFirstName);
+        Comparator<People> cmp2 = Comparators.comparing((Function<People, String>) People::getLastName);
+        Comparator<People> cmp = Comparators.compose(cmp1, cmp2);
+
+        assertPairComparison(people[0], people[0], people[1], people[1],
+                         Comparators.<People, People>byKey(cmp),
+                         Comparators.<People, People>byValue(cmp));
+
+    }
+
+    private <T> void assertComparison(Comparator<T> cmp, T less, T greater) {
+        assertTrue(cmp.compare(less, greater) < 0, "less");
+        assertTrue(cmp.compare(less, less) == 0, "equal");
+        assertTrue(cmp.compare(greater, less) > 0, "greater");
+    }
+
+    public void testComparatorDefaultMethods() {
+        Comparator<People> cmp = Comparators.comparing((Function<People, String>) People::getFirstName);
+        Comparator<People> cmp2 = Comparators.comparing((Function<People, String>) People::getLastName);
+        // reverseOrder
+        assertComparison(cmp.reverseOrder(), people[1], people[0]);
+        // thenComparing(Comparator)
+        assertComparison(cmp.thenComparing(cmp2), people[0], people[1]);
+        assertComparison(cmp.thenComparing(cmp2), people[4], people[0]);
+        // thenComparing(Function)
+        assertComparison(cmp.thenComparing(People::getLastName), people[0], people[1]);
+        assertComparison(cmp.thenComparing(People::getLastName), people[4], people[0]);
+        // thenComparing(ToIntFunction)
+        assertComparison(cmp.thenComparing(People::getAge), people[0], people[1]);
+        assertComparison(cmp.thenComparing(People::getAge), people[1], people[5]);
+        // thenComparing(ToLongFunction)
+        assertComparison(cmp.thenComparing(People::getAgeAsLong), people[0], people[1]);
+        assertComparison(cmp.thenComparing(People::getAgeAsLong), people[1], people[5]);
+        // thenComparing(ToDoubleFunction)
+        assertComparison(cmp.thenComparing(People::getAgeAsDouble), people[0], people[1]);
+        assertComparison(cmp.thenComparing(People::getAgeAsDouble), people[1], people[5]);
+    }
+
+    public void testGreaterOf() {
+        // lesser
+        assertSame(Comparators.greaterOf(Comparators.comparing(
+                                    (Function<People, String>) People::getFirstName))
+                              .apply(people[0], people[1]),
+                   people[1]);
+        // euqal
+        assertSame(Comparators.greaterOf(Comparators.comparing(
+                                    (Function<People, String>) People::getLastName))
+                              .apply(people[0], people[1]),
+                   people[0]);
+        // greater
+        assertSame(Comparators.greaterOf(Comparators.comparing(
+                                    (ToIntFunction<People>) People::getAge))
+                              .apply(people[0], people[1]),
+                   people[0]);
+    }
+
+    public void testLesserOf() {
+        // lesser
+        assertSame(Comparators.lesserOf(Comparators.comparing(
+                                    (Function<People, String>) People::getFirstName))
+                              .apply(people[0], people[1]),
+                   people[0]);
+        // euqal
+        assertSame(Comparators.lesserOf(Comparators.comparing(
+                                    (Function<People, String>) People::getLastName))
+                              .apply(people[0], people[1]),
+                   people[0]);
+        // greater
+        assertSame(Comparators.lesserOf(Comparators.comparing(
+                                    (ToIntFunction<People>) People::getAge))
+                              .apply(people[0], people[1]),
+                   people[1]);
+    }
+
+    public void testNulls() {
+        try {
+            Comparators.<String>naturalOrder().compare("abc", (String) null);
+            fail("expected NPE with naturalOrder");
+        } catch (NullPointerException npe) {}
+        try {
+            Comparators.<String>naturalOrder().compare((String) null, "abc");
+            fail("expected NPE with naturalOrder");
+        } catch (NullPointerException npe) {}
+
+        try {
+            Comparators.<String>reverseOrder().compare("abc", (String) null);
+            fail("expected NPE with naturalOrder");
+        } catch (NullPointerException npe) {}
+        try {
+            Comparators.<String>reverseOrder().compare((String) null, "abc");
+            fail("expected NPE with naturalOrder");
+        } catch (NullPointerException npe) {}
+
+        try {
+            Comparator<Map.Entry<String, String>> cmp = Comparators.byKey(null);
+            fail("byKey(null) should throw NPE");
+        } catch (NullPointerException npe) {}
+
+        try {
+            Comparator<Map.Entry<String, String>> cmp = Comparators.byValue(null);
+            fail("byValue(null) should throw NPE");
+        } catch (NullPointerException npe) {}
+
+        try {
+            Comparator<People> cmp = Comparators.comparing((Function<People, String>) null);
+            fail("comparing(null) should throw NPE");
+        } catch (NullPointerException npe) {}
+        try {
+            Comparator<People> cmp = Comparators.comparing((ToIntFunction<People>) null);
+            fail("comparing(null) should throw NPE");
+        } catch (NullPointerException npe) {}
+        try {
+            Comparator<People> cmp = Comparators.comparing((ToLongFunction<People>) null);
+            fail("comparing(null) should throw NPE");
+        } catch (NullPointerException npe) {}
+        try {
+            Comparator<People> cmp = Comparators.comparing((ToDoubleFunction<People>) null);
+            fail("comparing(null) should throw NPE");
+        } catch (NullPointerException npe) {}
+
+        try {
+            BinaryOperator<String> op = Comparators.lesserOf(null);
+            fail("lesserOf(null) should throw NPE");
+        } catch (NullPointerException npe) {}
+
+        try {
+            BinaryOperator<String> op = Comparators.greaterOf(null);
+            fail("lesserOf(null) should throw NPE");
+        } catch (NullPointerException npe) {}
+    }
+}

--- a/jdk/test/java/util/ComparatorsTest.java	Fri Apr 12 12:12:53 2013 -0700
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,353 +0,0 @@
-/*
- * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
- * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
- *
- * This code is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License version 2 only, as
- * published by the Free Software Foundation.
- *
- * This code is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
- * version 2 for more details (a copy is included in the LICENSE file that
- * accompanied this code).
- *
- * You should have received a copy of the GNU General Public License version
- * 2 along with this work; if not, write to the Free Software Foundation,
- * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
- *
- * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
- * or visit www.oracle.com if you need additional information or have any
- * questions.
- */
-
-/*
- * @test
- * @bug 8001667
- * @run testng ComparatorsTest
- */
-
-import java.util.Comparator;
-import java.util.Comparators;
-import java.util.AbstractMap;
-import java.util.Map;
-import org.testng.annotations.Test;
-
-import java.util.function.Function;
-import java.util.function.ToIntFunction;
-import java.util.function.ToLongFunction;
-import java.util.function.ToDoubleFunction;
-
-import static org.testng.Assert.assertEquals;
-import static org.testng.Assert.assertTrue;
-import static org.testng.Assert.assertSame;
-
-/**
- * Unit tests for helper methods in Comparators
- */
-@Test(groups = "unit")
-public class ComparatorsTest {
-    private static class Thing {
-        public final int intField;
-        public final long longField;
-        public final double doubleField;
-        public final String stringField;
-
-        private Thing(int intField, long longField, double doubleField, String stringField) {
-            this.intField = intField;
-            this.longField = longField;
-            this.doubleField = doubleField;
-            this.stringField = stringField;
-        }
-
-        public int getIntField() {
-            return intField;
-        }
-
-        public long getLongField() {
-            return longField;
-        }
-
-        public double getDoubleField() {
-            return doubleField;
-        }
-
-        public String getStringField() {
-            return stringField;
-        }
-    }
-
-    private final int[] intValues = { -2, -2, -1, -1, 0, 0, 1, 1, 2, 2 };
-    private final long[] longValues = { -2, -2, -1, -1, 0, 0, 1, 1, 2, 2 };
-    private final double[] doubleValues = { -2, -2, -1, -1, 0, 0, 1, 1, 2, 2 };
-    private final String[] stringValues = { "a", "a", "b", "b", "c", "c", "d", "d", "e", "e" };
-    private final int[] comparisons = { 0, -1, 0, -1, 0, -1, 0, -1, 0 };
-
-    private<T> void assertComparisons(T[] things, Comparator<T> comp, int[] comparisons) {
-        for (int i=0; i<comparisons.length; i++) {
-            assertEquals(comparisons.length + 1, things.length);
-            assertEquals(comparisons[i], comp.compare(things[i], things[i+1]));
-            assertEquals(-comparisons[i], comp.compare(things[i+1], things[i]));
-        }
-    }
-
-    public void testIntComparator() {
-        Thing[] things = new Thing[intValues.length];
-        for (int i=0; i<intValues.length; i++)
-            things[i] = new Thing(intValues[i], 0L, 0.0, null);
-        Comparator<Thing> comp = Comparators.comparing(new ToIntFunction<ComparatorsTest.Thing>() {
-            @Override
-            public int applyAsInt(Thing thing) {
-                return thing.getIntField();
-            }
-        });
-
-        assertComparisons(things, comp, comparisons);
-    }
-
-    public void testLongComparator() {
-        Thing[] things = new Thing[longValues.length];
-        for (int i=0; i<longValues.length; i++)
-            things[i] = new Thing(0, longValues[i], 0.0, null);
-        Comparator<Thing> comp = Comparators.comparing(new ToLongFunction<ComparatorsTest.Thing>() {
-            @Override
-            public long applyAsLong(Thing thing) {
-                return thing.getLongField();
-            }
-        });
-
-        assertComparisons(things, comp, comparisons);
-    }
-
-    public void testDoubleComparator() {
-        Thing[] things = new Thing[doubleValues.length];
-        for (int i=0; i<doubleValues.length; i++)
-            things[i] = new Thing(0, 0L, doubleValues[i], null);
-        Comparator<Thing> comp = Comparators.comparing(new ToDoubleFunction<ComparatorsTest.Thing>() {
-            @Override
-            public double applyAsDouble(Thing thing) {
-                return thing.getDoubleField();
-            }
-        });
-
-        assertComparisons(things, comp, comparisons);
-    }
-
-    public void testComparing() {
-        Thing[] things = new Thing[doubleValues.length];
-        for (int i=0; i<doubleValues.length; i++)
-            things[i] = new Thing(0, 0L, 0.0, stringValues[i]);
-        Comparator<Thing> comp = Comparators.comparing(new Function<Thing, String>() {
-            @Override
-            public String apply(Thing thing) {
-                return thing.getStringField();
-            }
-        });
-
-        assertComparisons(things, comp, comparisons);
-    }
-
-    public void testNaturalOrderComparator() {
-        Comparator<String> comp = Comparators.naturalOrder();
-
-        assertComparisons(stringValues, comp, comparisons);
-    }
-
-    public void testReverseComparator() {
-        Comparator<String> cmpr = Comparators.reverseOrder();
-        Comparator<String> cmp = cmpr.reverseOrder();
-
-        assertEquals(cmp.reverseOrder(), cmpr);
-        assertEquals(0, cmp.compare("a", "a"));
-        assertEquals(0, cmpr.compare("a", "a"));
-        assertTrue(cmp.compare("a", "b") < 0);
-        assertTrue(cmpr.compare("a", "b") > 0);
-        assertTrue(cmp.compare("b", "a") > 0);
-        assertTrue(cmpr.compare("b", "a") < 0);
-    }
-
-    public void testReverseComparator2() {
-        Comparator<String> cmp = (s1, s2) -> s1.length() - s2.length();
-        Comparator<String> cmpr = cmp.reverseOrder();
-
-        assertEquals(cmpr.reverseOrder(), cmp);
-        assertEquals(0, cmp.compare("abc", "def"));
-        assertEquals(0, cmpr.compare("abc", "def"));
-        assertTrue(cmp.compare("abcd", "def") > 0);
-        assertTrue(cmpr.compare("abcd", "def") < 0);
-        assertTrue(cmp.compare("abc", "defg") < 0);
-        assertTrue(cmpr.compare("abc", "defg") > 0);
-    }
-
-    @Test(expectedExceptions=NullPointerException.class)
-    public void testReverseComparatorNPE() {
-        Comparator<String> cmp = Comparators.reverseOrder(null);
-    }
-
-    public void testComposeComparator() {
-        // Longer string in front
-        Comparator<String> first = (s1, s2) -> s2.length() - s1.length();
-        Comparator<String> second = Comparators.naturalOrder();
-        Comparator<String> composed = Comparators.compose(first, second);
-
-        assertTrue(composed.compare("abcdefg", "abcdef") < 0);
-        assertTrue(composed.compare("abcdef", "abcdefg") > 0);
-        assertTrue(composed.compare("abcdef", "abcdef") == 0);
-        assertTrue(composed.compare("abcdef", "ghijkl") < 0);
-        assertTrue(composed.compare("ghijkl", "abcdefg") > 0);
-    }
-
-    private <K, V> void assertPairComparison(K k1, V v1, K k2, V v2,
-                                        Comparator<Map.Entry<K, V>> ck,
-                                        Comparator<Map.Entry<K, V>> cv) {
-        final Map.Entry<K, V> p11 = new AbstractMap.SimpleImmutableEntry<>(k1, v1);
-        final Map.Entry<K, V> p12 = new AbstractMap.SimpleImmutableEntry<>(k1, v2);
-        final Map.Entry<K, V> p21 = new AbstractMap.SimpleImmutableEntry<>(k2, v1);
-        final Map.Entry<K, V> p22 = new AbstractMap.SimpleImmutableEntry<>(k2, v2);
-
-        assertTrue(ck.compare(p11, p11) == 0);
-        assertTrue(ck.compare(p12, p11) == 0);
-        assertTrue(ck.compare(p11, p12) == 0);
-        assertTrue(ck.compare(p12, p22) < 0);
-        assertTrue(ck.compare(p12, p21) < 0);
-        assertTrue(ck.compare(p21, p11) > 0);
-        assertTrue(ck.compare(p21, p12) > 0);
-
-        assertTrue(cv.compare(p11, p11) == 0);
-        assertTrue(cv.compare(p12, p11) > 0);
-        assertTrue(cv.compare(p11, p12) < 0);
-        assertTrue(cv.compare(p12, p22) == 0);
-        assertTrue(cv.compare(p12, p21) > 0);
-        assertTrue(cv.compare(p21, p11) == 0);
-        assertTrue(cv.compare(p21, p12) < 0);
-
-        Comparator<Map.Entry<K, V>> cmp = Comparators.compose(ck, cv);
-        assertTrue(cmp.compare(p11, p11) == 0);
-        assertTrue(cmp.compare(p12, p11) > 0);
-        assertTrue(cmp.compare(p11, p12) < 0);
-        assertTrue(cmp.compare(p12, p22) < 0);
-        assertTrue(cmp.compare(p12, p21) < 0);
-        assertTrue(cmp.compare(p21, p11) > 0);
-        assertTrue(cmp.compare(p21, p12) > 0);
-
-        cmp = Comparators.compose(cv, ck);
-        assertTrue(cmp.compare(p11, p11) == 0);
-        assertTrue(cmp.compare(p12, p11) > 0);
-        assertTrue(cmp.compare(p11, p12) < 0);
-        assertTrue(cmp.compare(p12, p22) < 0);
-        assertTrue(cmp.compare(p12, p21) > 0);
-        assertTrue(cmp.compare(p21, p11) > 0);
-        assertTrue(cmp.compare(p21, p12) < 0);
-    }
-
-    public void testKVComparatorable() {
-        assertPairComparison(1, "ABC", 2, "XYZ",
-                         Comparators.<Integer, String>naturalOrderKeys(),
-                         Comparators.<Integer, String>naturalOrderValues());
-    }
-
-    private static class People {
-        final String firstName;
-        final String lastName;
-        final int age;
-
-        People(String first, String last, int age) {
-            firstName = first;
-            lastName = last;
-            this.age = age;
-        }
-
-        String getFirstName() { return firstName; }
-        String getLastName() { return lastName; }
-        int getAge() { return age; }
-        long getAgeAsLong() { return (long) age; };
-        double getAgeAsDouble() { return (double) age; };
-    }
-
-    private final People people[] = {
-        new People("John", "Doe", 34),
-        new People("Mary", "Doe", 30),
-        new People("Maria", "Doe", 14),
-        new People("Jonah", "Doe", 10),
-        new People("John", "Cook", 54),
-        new People("Mary", "Cook", 50),
-    };
-
-    public void testKVComparators() {
-        // Comparator<People> cmp = Comparators.naturalOrder(); // Should fail to compiler as People is not comparable
-        // We can use simple comparator, but those have been tested above.
-        // Thus choose to do compose for some level of interation.
-        Comparator<People> cmp1 = Comparators.comparing((Function<People, String>) People::getFirstName);
-        Comparator<People> cmp2 = Comparators.comparing((Function<People, String>) People::getLastName);
-        Comparator<People> cmp = Comparators.compose(cmp1, cmp2);
-
-        assertPairComparison(people[0], people[0], people[1], people[1],
-                         Comparators.<People, People>byKey(cmp),
-                         Comparators.<People, People>byValue(cmp));
-
-    }
-
-    private <T> void assertComparison(Comparator<T> cmp, T less, T greater) {
-        assertTrue(cmp.compare(less, greater) < 0, "less");
-        assertTrue(cmp.compare(less, less) == 0, "equal");
-        assertTrue(cmp.compare(greater, less) > 0, "greater");
-    }
-
-    public void testComparatorDefaultMethods() {
-        Comparator<People> cmp = Comparators.comparing((Function<People, String>) People::getFirstName);
-        Comparator<People> cmp2 = Comparators.comparing((Function<People, String>) People::getLastName);
-        // reverseOrder
-        assertComparison(cmp.reverseOrder(), people[1], people[0]);
-        // thenComparing(Comparator)
-        assertComparison(cmp.thenComparing(cmp2), people[0], people[1]);
-        assertComparison(cmp.thenComparing(cmp2), people[4], people[0]);
-        // thenComparing(Function)
-        assertComparison(cmp.thenComparing(People::getLastName), people[0], people[1]);
-        assertComparison(cmp.thenComparing(People::getLastName), people[4], people[0]);
-        // thenComparing(ToIntFunction)
-        assertComparison(cmp.thenComparing(People::getAge), people[0], people[1]);
-        assertComparison(cmp.thenComparing(People::getAge), people[1], people[5]);
-        // thenComparing(ToLongFunction)
-        assertComparison(cmp.thenComparing(People::getAgeAsLong), people[0], people[1]);
-        assertComparison(cmp.thenComparing(People::getAgeAsLong), people[1], people[5]);
-        // thenComparing(ToDoubleFunction)
-        assertComparison(cmp.thenComparing(People::getAgeAsDouble), people[0], people[1]);
-        assertComparison(cmp.thenComparing(People::getAgeAsDouble), people[1], people[5]);
-    }
-
-    public void testGreaterOf() {
-        // lesser
-        assertSame(Comparators.greaterOf(Comparators.comparing(
-                                    (Function<People, String>) People::getFirstName))
-                              .apply(people[0], people[1]),
-                   people[1]);
-        // euqal
-        assertSame(Comparators.greaterOf(Comparators.comparing(
-                                    (Function<People, String>) People::getLastName))
-                              .apply(people[0], people[1]),
-                   people[0]);
-        // greater
-        assertSame(Comparators.greaterOf(Comparators.comparing(
-                                    (ToIntFunction<People>) People::getAge))
-                              .apply(people[0], people[1]),
-                   people[0]);
-    }
-
-    public void testLesserOf() {
-        // lesser
-        assertSame(Comparators.lesserOf(Comparators.comparing(
-                                    (Function<People, String>) People::getFirstName))
-                              .apply(people[0], people[1]),
-                   people[0]);
-        // euqal
-        assertSame(Comparators.lesserOf(Comparators.comparing(
-                                    (Function<People, String>) People::getLastName))
-                              .apply(people[0], people[1]),
-                   people[0]);
-        // greater
-        assertSame(Comparators.lesserOf(Comparators.comparing(
-                                    (ToIntFunction<People>) People::getAge))
-                              .apply(people[0], people[1]),
-                   people[1]);
-    }
-}
\ No newline at end of file