COLLECTIONS-788 - java8 improvements: (#228)

* Replace Collections.sort() with List.sort()
* Replace lambda with method reference
* Replace Loop with Collection.removeIf()
* Use lambda

Co-authored-by: Gary Gregory <garydgregory@users.noreply.github.com>

src/test/java/org/apache/commons/collections4/FluentIterableTest.java

@@ -213,7 +213,7 @@ public class FluentIterableTest {
     @Test
     public void forEach() {
         final AtomicInteger sum = new AtomicInteger(0);
-        final Closure<Integer> closure = input -> sum.addAndGet(input);
+        final Closure<Integer> closure = sum::addAndGet;
 
         FluentIterable.of(iterableA).forEach(closure);
         int expectedSum = 0;

src/test/java/org/apache/commons/collections4/MapUtilsTest.java

@@ -167,9 +167,7 @@ public class MapUtilsTest {
     @Test
     public void testInvertMapNull() {
         final Map<String, String> nullMap = null;
-        final Exception exception = assertThrows(NullPointerException.class, () -> {
-            MapUtils.invertMap(nullMap);
-        });
+        final Exception exception = assertThrows(NullPointerException.class, () -> MapUtils.invertMap(nullMap));
         final String actualMessage = exception.getMessage();
         assertTrue(actualMessage.contains("map"));
     }
@@ -1015,30 +1013,22 @@ public class MapUtilsTest {
 
     @Test
     public void testUnmodifiableMap() {
-        final Exception exception = assertThrows(UnsupportedOperationException.class, () -> {
-            MapUtils.unmodifiableMap(new HashMap<>()).clear();
-        });
+        final Exception exception = assertThrows(UnsupportedOperationException.class, () -> MapUtils.unmodifiableMap(new HashMap<>()).clear());
     }
 
     @Test
     public void testUnmodifiableSortedMap() {
-        final Exception exception = assertThrows(UnsupportedOperationException.class, () -> {
-            MapUtils.unmodifiableSortedMap(new TreeMap<>()).clear();
-        });
+        final Exception exception = assertThrows(UnsupportedOperationException.class, () -> MapUtils.unmodifiableSortedMap(new TreeMap<>()).clear());
     }
 
     @Test
     public void testFixedSizeMap() {
-        final Exception exception = assertThrows(IllegalArgumentException.class, () -> {
-            MapUtils.fixedSizeMap(new HashMap<>()).put(new Object(), new Object());
-        });
+        final Exception exception = assertThrows(IllegalArgumentException.class, () -> MapUtils.fixedSizeMap(new HashMap<>()).put(new Object(), new Object()));
     }
 
     @Test
     public void testFixedSizeSortedMap() {
-        final Exception exception = assertThrows(IllegalArgumentException.class, () -> {
-            MapUtils.fixedSizeSortedMap(new TreeMap<Long, Long>()).put(1L, 1L);
-        });
+        final Exception exception = assertThrows(IllegalArgumentException.class, () -> MapUtils.fixedSizeSortedMap(new TreeMap<Long, Long>()).put(1L, 1L));
     }
 
     @Test

src/test/java/org/apache/commons/collections4/SplitMapUtilsTest.java

@@ -79,7 +79,7 @@ public class SplitMapUtilsTest {
         // check individual operations
         int sz = map.size();
 
-        attemptPutOperation(() -> map.clear());
+        attemptPutOperation(map::clear);
 
         assertEquals(sz, map.size());
 
@@ -116,11 +116,11 @@ public class SplitMapUtilsTest {
     public void testWritableMap() {
         final Map<String, String> map = SplitMapUtils.writableMap(transformedMap);
         attemptGetOperation(() -> map.get(null));
-        attemptGetOperation(() -> map.entrySet());
-        attemptGetOperation(() -> map.keySet());
-        attemptGetOperation(() -> map.values());
-        attemptGetOperation(() -> map.size());
-        attemptGetOperation(() -> map.isEmpty());
+        attemptGetOperation(map::entrySet);
+        attemptGetOperation(map::keySet);
+        attemptGetOperation(map::values);
+        attemptGetOperation(map::size);
+        attemptGetOperation(map::isEmpty);
         attemptGetOperation(() -> map.containsKey(null));
         attemptGetOperation(() -> map.containsValue(null));
         attemptGetOperation(() -> map.remove(null));

src/test/java/org/apache/commons/collections4/collection/AbstractCollectionTest.java

@@ -963,7 +963,7 @@ public abstract class AbstractCollectionTest<E> extends AbstractObjectTest {
         final int size = getCollection().size();
         final int targetCount = Collections.frequency(elements, target);
 
-        final Predicate<E> filter = e -> target.equals(e);
+        final Predicate<E> filter = target::equals;
 
         assertTrue("Full collection removeIf should work", getCollection().removeIf(filter));
         getConfirmed().removeIf(filter);

src/test/java/org/apache/commons/collections4/map/LRUMapTest.java

@@ -700,12 +700,7 @@ public class LRUMapTest<K, V> extends AbstractOrderedMapTest<K, V> {
                             }
                         }
                         synchronized (map) {
-                            for (final Iterator<Map.Entry<Object, Thread>> iter = map.entrySet().iterator(); iter.hasNext();) {
-                                final Map.Entry<Object, Thread> entry = iter.next();
-                                if (entry.getValue() == this) {
-                                    iter.remove();
-                                }
-                            }
+                            map.entrySet().removeIf(entry -> entry.getValue() == this);
                         }
                     } catch (final InterruptedException e) {
                         fail("Unexpected InterruptedException");
@@ -866,11 +861,7 @@ public class LRUMapTest<K, V> extends AbstractOrderedMapTest<K, V> {
                             }
                         }
                         synchronized (map) {
-                            for (final Iterator<Thread> iter = map.values().iterator(); iter.hasNext();) {
-                                if (iter.next() == this) {
-                                    iter.remove();
-                                }
-                            }
+                            map.values().removeIf(thread1 -> thread1 == this);
                         }
                     } catch (final InterruptedException e) {
                         fail("Unexpected InterruptedException");

src/test/java/org/apache/commons/collections4/map/ReferenceMapTest.java

@@ -261,7 +261,7 @@ public class ReferenceMapTest<K, V> extends AbstractIterableMapTest<K, V> {
     public void testCustomPurge() {
         final List<Integer> expiredValues = new ArrayList<>();
         @SuppressWarnings("unchecked")
-        final Consumer<Integer> consumer = (Consumer<Integer> & Serializable) v -> expiredValues.add(v);
+        final Consumer<Integer> consumer = (Consumer<Integer> & Serializable) expiredValues::add;
         final Map<Integer, Integer> map = new ReferenceMap<Integer, Integer>(ReferenceStrength.WEAK, ReferenceStrength.HARD, false) {
             private static final long serialVersionUID = 1L;