Don't initialize an instance variable to its default value

src/conf/checkstyle.xml

@@ -42,6 +42,7 @@ limitations under the License.
     <property name="headerFile" value="${checkstyle.header.file}"/>
   </module>
   <module name="TreeWalker">
+    <module name="ExplicitInitializationCheck" />
     <module name="AvoidStarImport"/>
     <module name="IllegalImport"/>
     <module name="RedundantImport"/>

src/main/java/org/apache/commons/collections4/bloomfilter/CountingLongPredicate.java

@@ -25,7 +25,7 @@
  * execute the @code{text} with a zero value for each remaining @{code idx} value.
  */
 class CountingLongPredicate implements LongPredicate {
-    private int idx = 0;
+    private int idx;
     private final long[] ary;
     private final LongBiPredicate func;
 

src/main/java/org/apache/commons/collections4/bloomfilter/IndexProducer.java

@@ -82,7 +82,7 @@ static IndexProducer fromBitMapProducer(final BitMapProducer producer) {
         Objects.requireNonNull(producer, "producer");
         return consumer -> {
             final LongPredicate longPredicate = new LongPredicate() {
-                int wordIdx = 0;
+                int wordIdx;
 
                 @Override
                 public boolean test(long word) {

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

@@ -45,7 +45,7 @@ public class ClosureUtilsTest {
     private static final Object cString = "Hello";
 
     static class MockClosure<T> implements Closure<T> {
-        int count = 0;
+        int count;
 
         @Override
         public void execute(final T object) {
@@ -58,7 +58,7 @@ public void reset() {
     }
 
     static class MockTransformer<T> implements Transformer<T, T> {
-        int count = 0;
+        int count;
 
         @Override
         public T transform(final T object) {

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

@@ -69,54 +69,54 @@ public class CollectionUtilsTest extends MockTestCase {
     /**
      * Collection of {@link Integer}s
      */
-    private List<Integer> collectionA = null;
+    private List<Integer> collectionA;
 
     /**
      * Collection of {@link Long}s
      */
-    private List<Long> collectionB = null;
+    private List<Long> collectionB;
 
     /**
      * Collection of {@link Integer}s that are equivalent to the Longs in
      * collectionB.
      */
-    private Collection<Integer> collectionC = null;
+    private Collection<Integer> collectionC;
 
     /**
      * Sorted Collection of {@link Integer}s
      */
-    private Collection<Integer> collectionD = null;
+    private Collection<Integer> collectionD;
 
     /**
      * Sorted Collection of {@link Integer}s
      */
-    private Collection<Integer> collectionE = null;
+    private Collection<Integer> collectionE;
 
     /**
      * Collection of {@link Integer}s, bound as {@link Number}s
      */
-    private Collection<Number> collectionA2 = null;
+    private Collection<Number> collectionA2;
 
     /**
      * Collection of {@link Long}s, bound as {@link Number}s
      */
-    private Collection<Number> collectionB2 = null;
+    private Collection<Number> collectionB2;
 
     /**
      * Collection of {@link Integer}s (cast as {@link Number}s) that are
      * equivalent to the Longs in collectionB.
      */
-    private Collection<Number> collectionC2 = null;
+    private Collection<Number> collectionC2;
 
-    private Iterable<Integer> iterableA = null;
+    private Iterable<Integer> iterableA;
 
-    private Iterable<Long> iterableB = null;
+    private Iterable<Long> iterableB;
 
-    private Iterable<Integer> iterableC = null;
+    private Iterable<Integer> iterableC;
 
-    private Iterable<Number> iterableA2 = null;
+    private Iterable<Number> iterableA2;
 
-    private Iterable<Number> iterableB2 = null;
+    private Iterable<Number> iterableB2;
 
     private final Collection<Integer> emptyCollection = new ArrayList<>(1);
 

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

@@ -168,7 +168,7 @@ public int hashCode() { // please Findbugs
     }
 
     public static class Mock3 {
-        private static int cCounter = 0;
+        private static int cCounter;
         private final int iVal;
         public Mock3() {
             iVal = cCounter++;

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

@@ -47,27 +47,27 @@ public class FluentIterableTest {
     /**
      * Iterable of {@link Integer}s
      */
-    private Iterable<Integer> iterableA = null;
+    private Iterable<Integer> iterableA;
 
     /**
      * Iterable of {@link Long}s
      */
-    private Iterable<Long> iterableB = null;
+    private Iterable<Long> iterableB;
 
     /**
      * Collection of even {@link Integer}s
      */
-    private Iterable<Integer> iterableEven = null;
+    private Iterable<Integer> iterableEven;
 
     /**
      * Collection of odd {@link Integer}s
      */
-    private Iterable<Integer> iterableOdd = null;
+    private Iterable<Integer> iterableOdd;
 
     /**
      * An empty Iterable.
      */
-    private Iterable<Integer> emptyIterable = null;
+    private Iterable<Integer> emptyIterable;
 
     @BeforeEach
     public void setUp() {

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

@@ -50,17 +50,17 @@ public class IterableUtilsTest {
     /**
      * Iterable of {@link Integer}s
      */
-    private Iterable<Integer> iterableA = null;
+    private Iterable<Integer> iterableA;
 
     /**
      * Iterable of {@link Long}s
      */
-    private Iterable<Long> iterableB = null;
+    private Iterable<Long> iterableB;
 
     /**
      * An empty Iterable.
      */
-    private Iterable<Integer> emptyIterable = null;
+    private Iterable<Integer> emptyIterable;
 
     @BeforeEach
     public void setUp() {

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

@@ -70,21 +70,21 @@ public class IteratorUtilsTest {
     /**
      * Collection of {@link Integer}s
      */
-    private List<Integer> collectionA = null;
+    private List<Integer> collectionA;
 
     /**
      * Collection of even {@link Integer}s
      */
-    private List<Integer> collectionEven = null;
+    private List<Integer> collectionEven;
 
     /**
      * Collection of odd {@link Integer}s
      */
-    private List<Integer> collectionOdd = null;
+    private List<Integer> collectionOdd;
 
     private final Collection<Integer> emptyCollection = new ArrayList<>(1);
 
-    private Iterable<Integer> iterableA = null;
+    private Iterable<Integer> iterableA;
 
     /**
      * Creates a NodeList containing the specified nodes.

src/test/java/org/apache/commons/collections4/bidimap/AbstractOrderedBidiMapDecoratorTest.java

@@ -67,7 +67,7 @@ public boolean isSetValueSupported() {
      */
     private static final class TestOrderedBidiMap<K, V> extends AbstractOrderedBidiMapDecorator<K, V> {
 
-        private TestOrderedBidiMap<V, K> inverse = null;
+        private TestOrderedBidiMap<V, K> inverse;
 
         TestOrderedBidiMap() {
             super(new DualTreeBidiMap<>());

src/test/java/org/apache/commons/collections4/iterators/CollatingIteratorTest.java

@@ -45,10 +45,10 @@ public CollatingIteratorTest() {
 
     //--------------------------------------------------------------- Lifecycle
 
-    private Comparator<Integer> comparator = null;
-    private ArrayList<Integer> evens = null;
-    private ArrayList<Integer> odds = null;
-    private ArrayList<Integer> fib = null;
+    private Comparator<Integer> comparator;
+    private ArrayList<Integer> evens;
+    private ArrayList<Integer> odds;
+    private ArrayList<Integer> fib;
 
     @BeforeEach
     public void setUp() throws Exception {

src/test/java/org/apache/commons/collections4/iterators/FilterListIteratorTest.java

@@ -39,18 +39,18 @@
 @SuppressWarnings("boxing")
 public class FilterListIteratorTest {
 
-    private ArrayList<Integer> list = null;
-    private ArrayList<Integer> odds = null;
-    private ArrayList<Integer> evens = null;
-    private ArrayList<Integer> threes = null;
-    private ArrayList<Integer> fours = null;
-    private ArrayList<Integer> sixes = null;
-    private Predicate<Integer> truePred = null;
-    private Predicate<Integer> falsePred = null;
-    private Predicate<Integer> evenPred = null;
-    private Predicate<Integer> oddPred = null;
-    private Predicate<Integer> threePred = null;
-    private Predicate<Integer> fourPred = null;
+    private ArrayList<Integer> list;
+    private ArrayList<Integer> odds;
+    private ArrayList<Integer> evens;
+    private ArrayList<Integer> threes;
+    private ArrayList<Integer> fours;
+    private ArrayList<Integer> sixes;
+    private Predicate<Integer> truePred;
+    private Predicate<Integer> falsePred;
+    private Predicate<Integer> evenPred;
+    private Predicate<Integer> oddPred;
+    private Predicate<Integer> threePred;
+    private Predicate<Integer> fourPred;
     private final Random random = new Random();
 
     @BeforeEach

src/test/java/org/apache/commons/collections4/iterators/IteratorChainTest.java

@@ -41,9 +41,9 @@ public class IteratorChainTest extends AbstractIteratorTest<String> {
         "One", "Two", "Three", "Four", "Five", "Six"
     };
 
-    protected List<String> list1 = null;
-    protected List<String> list2 = null;
-    protected List<String> list3 = null;
+    protected List<String> list1;
+    protected List<String> list2;
+    protected List<String> list3;
 
     public IteratorChainTest() {
         super(IteratorChainTest.class.getSimpleName());

src/test/java/org/apache/commons/collections4/iterators/LazyIteratorChainTest.java

@@ -41,9 +41,9 @@ public class LazyIteratorChainTest extends AbstractIteratorTest<String> {
         "One", "Two", "Three", "Four", "Five", "Six"
     };
 
-    protected List<String> list1 = null;
-    protected List<String> list2 = null;
-    protected List<String> list3 = null;
+    protected List<String> list1;
+    protected List<String> list2;
+    protected List<String> list3;
 
     public LazyIteratorChainTest() {
         super(LazyIteratorChainTest.class.getSimpleName());

src/test/java/org/apache/commons/collections4/iterators/ListIteratorWrapper2Test.java

@@ -38,7 +38,7 @@ public class ListIteratorWrapper2Test<E> extends AbstractIteratorTest<E> {
         "One", "Two", "Three", "Four", "Five", "Six"
     };
 
-    protected List<E> list1 = null;
+    protected List<E> list1;
 
     public ListIteratorWrapper2Test() {
         super(ListIteratorWrapper2Test.class.getSimpleName());

src/test/java/org/apache/commons/collections4/iterators/ListIteratorWrapperTest.java

@@ -39,7 +39,7 @@ public class ListIteratorWrapperTest<E> extends AbstractIteratorTest<E> {
         "One", "Two", "Three", "Four", "Five", "Six"
     };
 
-    protected List<E> list1 = null;
+    protected List<E> list1;
 
     public ListIteratorWrapperTest() {
         super(ListIteratorWrapperTest.class.getSimpleName());

src/test/java/org/apache/commons/collections4/iterators/ObjectGraphIteratorTest.java

@@ -39,10 +39,10 @@ public class ObjectGraphIteratorTest extends AbstractIteratorTest<Object> {
 
     protected String[] testArray = { "One", "Two", "Three", "Four", "Five", "Six" };
 
-    protected List<String> list1 = null;
-    protected List<String> list2 = null;
-    protected List<String> list3 = null;
-    protected List<Iterator<String>> iteratorList = null;
+    protected List<String> list1;
+    protected List<String> list2;
+    protected List<String> list3;
+    protected List<Iterator<String>> iteratorList;
 
     public ObjectGraphIteratorTest() {
         super(ObjectGraphIteratorTest.class.getSimpleName());

src/test/java/org/apache/commons/collections4/iterators/UniqueFilterIteratorTest.java

@@ -36,7 +36,7 @@ public class UniqueFilterIteratorTest<E> extends AbstractIteratorTest<E> {
         "One", "Two", "Three", "Four", "Five", "Six"
     };
 
-    protected List<E> list1 = null;
+    protected List<E> list1;
 
     public UniqueFilterIteratorTest() {
         super(UniqueFilterIteratorTest.class.getSimpleName());

src/test/java/org/apache/commons/collections4/iterators/ZippingIteratorTest.java

@@ -40,9 +40,9 @@ public ZippingIteratorTest() {
 
     //--------------------------------------------------------------- Lifecycle
 
-    private ArrayList<Integer> evens = null;
-    private ArrayList<Integer> odds = null;
-    private ArrayList<Integer> fib = null;
+    private ArrayList<Integer> evens;
+    private ArrayList<Integer> odds;
+    private ArrayList<Integer> fib;
 
     @BeforeEach
     public void setUp() throws Exception {

src/test/java/org/apache/commons/collections4/set/UnmodifiableNavigableSetTest.java

@@ -36,8 +36,8 @@
  * @since 4.1
  */
 public class UnmodifiableNavigableSetTest<E> extends AbstractNavigableSetTest<E> {
-    protected UnmodifiableNavigableSet<E> set = null;
-    protected ArrayList<E> array = null;
+    protected UnmodifiableNavigableSet<E> set;
+    protected ArrayList<E> array;
 
     public UnmodifiableNavigableSetTest() {
         super(UnmodifiableNavigableSetTest.class.getSimpleName());

src/test/java/org/apache/commons/collections4/set/UnmodifiableSortedSetTest.java

@@ -37,8 +37,8 @@
  * @since 3.0
  */
 public class UnmodifiableSortedSetTest<E> extends AbstractSortedSetTest<E> {
-    protected UnmodifiableSortedSet<E> set = null;
-    protected ArrayList<E> array = null;
+    protected UnmodifiableSortedSet<E> set;
+    protected ArrayList<E> array;
 
     public UnmodifiableSortedSetTest() {
         super(UnmodifiableSortedSetTest.class.getSimpleName());