Minor code cleanup (closes #1972)

src/main/java/org/assertj/core/api/AbstractDoubleAssert.java

@@ -46,12 +46,12 @@
 public abstract class AbstractDoubleAssert<SELF extends AbstractDoubleAssert<SELF>> extends
     AbstractComparableAssert<SELF, Double> implements FloatingPointNumberAssert<SELF, Double> {
 
-  private static final Double NEGATIVE_ZERO = Double.valueOf(-0.0);
+  private static final Double NEGATIVE_ZERO = -0.0;
 
   @VisibleForTesting
   Doubles doubles = Doubles.instance();
 
-  private boolean isPrimitive;
+  private final boolean isPrimitive;
 
   public AbstractDoubleAssert(Double actual, Class<?> selfType) {
     super(actual, selfType);

src/main/java/org/assertj/core/api/AbstractFloatAssert.java

@@ -44,12 +44,12 @@
 public abstract class AbstractFloatAssert<SELF extends AbstractFloatAssert<SELF>> extends AbstractComparableAssert<SELF, Float>
     implements FloatingPointNumberAssert<SELF, Float> {
 
-  private static final Float NEGATIVE_ZERO = Float.valueOf(-0.0f);
+  private static final Float NEGATIVE_ZERO = -0.0f;
 
   @VisibleForTesting
   Floats floats = Floats.instance();
 
-  private boolean isPrimitive;
+  private final boolean isPrimitive;
 
   public AbstractFloatAssert(Float actual, Class<?> selfType) {
     super(actual, selfType);

src/main/java/org/assertj/core/api/AbstractIterableAssert.java

@@ -2826,7 +2826,7 @@ private ELEMENT_ASSERT internalElement(int index) {
     isNotEmpty();
     assertThat(index).describedAs(navigationDescription("check index validity"))
                      .isBetween(0, IterableUtil.sizeOf(actual) - 1);
-    ELEMENT elementAtIndex = null;
+    ELEMENT elementAtIndex;
     if (actual instanceof List) {
       @SuppressWarnings("unchecked")
       List<? extends ELEMENT> list = (List<? extends ELEMENT>) actual;

src/main/java/org/assertj/core/error/BasicErrorMessageFactory.java

@@ -22,6 +22,7 @@
 import static org.assertj.core.util.Strings.quote;
 
 import java.util.Arrays;
+import java.util.Objects;
 
 import org.assertj.core.description.Description;
 import org.assertj.core.presentation.Representation;
@@ -85,7 +86,7 @@ public boolean equals(Object obj) {
       if (obj == null) return false;
       if (getClass() != obj.getClass()) return false;
       UnquotedString other = (UnquotedString) obj;
-      return string == null ? other.string == null : string.equals(other.string);
+      return Objects.equals(string, other.string);
     }
   }
 

src/main/java/org/assertj/core/internal/Comparables.java

@@ -92,7 +92,7 @@ public boolean equals(Object obj) {
     if (comparisonStrategy == null) {
       if (other.comparisonStrategy != null) return false;
     } else if (!comparisonStrategy.equals(other.comparisonStrategy)) return false;
-    return failures == null ? other.failures == null : failures.equals(other.failures);
+    return java.util.Objects.equals(failures, other.failures);
   }
 
   @Override

src/main/java/org/assertj/core/internal/FieldByFieldComparator.java

@@ -45,7 +45,7 @@ public FieldByFieldComparator(Map<String, Comparator<?>> comparatorsByPropertyOr
   }
 
   public FieldByFieldComparator() {
-    this(new TreeMap<String, Comparator<?>>(), defaultTypeComparators());
+    this(new TreeMap<>(), defaultTypeComparators());
   }
 
   @Override

src/main/java/org/assertj/core/internal/IgnoringFieldsComparator.java

@@ -24,7 +24,7 @@
 
 public class IgnoringFieldsComparator extends FieldByFieldComparator {
 
-  private String[] fields;
+  private final String[] fields;
 
   public IgnoringFieldsComparator(Map<String, Comparator<?>> comparatorByPropertyOrField,
                                   TypeComparators comparatorByType, String... fields) {
@@ -33,7 +33,7 @@ public IgnoringFieldsComparator(Map<String, Comparator<?>> comparatorByPropertyO
   }
 
   public IgnoringFieldsComparator(String... fields) {
-    this(new HashMap<String, Comparator<?>>(), defaultTypeComparators(), fields);
+    this(new HashMap<>(), defaultTypeComparators(), fields);
   }
 
   @VisibleForTesting

src/main/java/org/assertj/core/internal/OnFieldsComparator.java

@@ -27,7 +27,7 @@
 
 public class OnFieldsComparator extends FieldByFieldComparator {
 
-  private String[] fields;
+  private final String[] fields;
 
   public OnFieldsComparator(Map<String, Comparator<?>> comparatorByPropertyOrField,
                             TypeComparators comparatorByType, String... fields) {
@@ -42,7 +42,7 @@ public OnFieldsComparator(Map<String, Comparator<?>> comparatorByPropertyOrField
   }
 
   public OnFieldsComparator(String... fields) {
-    this(new HashMap<String, Comparator<?>>(), defaultTypeComparators(), fields);
+    this(new HashMap<>(), defaultTypeComparators(), fields);
   }
 
   @VisibleForTesting

src/main/java/org/assertj/core/util/Throwables.java

@@ -64,7 +64,7 @@ public static List<String> describeErrors(List<? extends Throwable> errors) {
   public static void appendStackTraceInCurrentThreadToThrowable(Throwable t, String methodToStartFrom) {
     List<StackTraceElement> stackTrace = newArrayList(t.getStackTrace());
     stackTrace.addAll(stackTraceInCurrentThread(methodToStartFrom));
-    t.setStackTrace(stackTrace.toArray(new StackTraceElement[stackTrace.size()]));
+    t.setStackTrace(stackTrace.toArray(new StackTraceElement[0]));
   }
 
   private static List<StackTraceElement> stackTraceInCurrentThread(String methodToStartFrom) {
@@ -130,7 +130,7 @@ public static void removeAssertJRelatedElementsFromStackTrace(Throwable throwabl
       }
       previous = element;
     }
-    StackTraceElement[] newStackTrace = filtered.toArray(new StackTraceElement[filtered.size()]);
+    StackTraceElement[] newStackTrace = filtered.toArray(new StackTraceElement[0]);
     throwable.setStackTrace(newStackTrace);
   }
 

src/main/java/org/assertj/core/util/diff/DiffUtils.java

@@ -46,7 +46,7 @@ public class DiffUtils {
    *         revised sequences. Never {@code null}.
    */
   public static <T> Patch<T> diff(List<T> original, List<T> revised) {
-    return DiffUtils.diff(original, revised, new MyersDiff<T>());
+    return DiffUtils.diff(original, revised, new MyersDiff<>());
   }
 
   /**