Fail-fast for a null DiffBuilder in

ReflectionDiffBuilder.ReflectionDiffBuilder(DiffBuilder, String[])
instead of getting a NullPointerException in ReflectionDiffBuilder
instance methods

- Merge if statements with the same return value
- Remove unnecessary null check

Author: garydgregory

src/changes/changes.xml

@@ -65,6 +65,7 @@ The <action> type attribute can be add,update,fix,remove.
     <action issue="LANG-1793" type="fix" dev="ggregory" due-to="IcoreE">Fix Javadoc description in CharUtils.isAsciiAlphanumeric() #1501.</action>
     <action issue="LANG-1794" type="fix" dev="ggregory" due-to="IcoreE">Fix Javadoc for RandomUtils.secure(), it incorrectly mentions securerandom.strongAlgorithms #1503.</action>
     <action                   type="fix" dev="ggregory" due-to="Gary Gregory">Fix NullPointerException in ReflectionDiffBuilder.getExcludeFieldNames() when instance created with ReflectionDiffBuilder.ReflectionDiffBuilder(T, T, ToStringStyle).</action>
+    <action                   type="fix" dev="ggregory" due-to="Gary Gregory">Fail-fast for a null DiffBuilder in ReflectionDiffBuilder.ReflectionDiffBuilder(DiffBuilder, String[]) instead of getting a NullPointerException in ReflectionDiffBuilder instance methods.</action>
     <!-- ADD -->
     <!-- UPDATE -->
     <action                   type="update" dev="ggregory" due-to="Gary Gregory, Dependabot">Bump org.apache.commons:commons-parent from 92 to 93 #1498.</action>

src/main/java/org/apache/commons/lang3/builder/ReflectionDiffBuilder.java

@@ -154,9 +154,16 @@ private static String[] toExcludeFieldNames(final String[] excludeFieldNames) {
      */
     private String[] excludeFieldNames;
 
+    /**
+     * Constructs a new instance.
+     *
+     * @param diffBuilder a non-null DiffBuilder.
+     * @param excludeFieldNames a non-null String array.
+     * @throw NullPointerException Thrown on null input.
+     */
     private ReflectionDiffBuilder(final DiffBuilder<T> diffBuilder, final String[] excludeFieldNames) {
-        this.diffBuilder = diffBuilder;
-        this.excludeFieldNames = Objects.requireNonNull(excludeFieldNames);
+        this.diffBuilder = Objects.requireNonNull(diffBuilder, "diffBuilder");
+        this.excludeFieldNames = Objects.requireNonNull(excludeFieldNames, "excludeFieldNames");
     }
 
     /**
@@ -179,17 +186,9 @@ public ReflectionDiffBuilder(final T left, final T right, final ToStringStyle st
     }
 
     private boolean accept(final Field field) {
-        if (field.getName().indexOf(ClassUtils.INNER_CLASS_SEPARATOR_CHAR) != -1) {
-            return false;
-        }
-        if (Modifier.isTransient(field.getModifiers())) {
-            return false;
-        }
-        if (Modifier.isStatic(field.getModifiers())) {
-            return false;
-        }
-        if (excludeFieldNames != null && Arrays.binarySearch(excludeFieldNames, field.getName()) >= 0) {
-            // Reject fields from the getExcludeFieldNames list.
+        if (field.getName().indexOf(ClassUtils.INNER_CLASS_SEPARATOR_CHAR) != -1 || Modifier.isTransient(field.getModifiers())
+                || Modifier.isStatic(field.getModifiers()) || Arrays.binarySearch(excludeFieldNames, field.getName()) >= 0) {
+            // Rejected.
             return false;
         }
         return !field.isAnnotationPresent(DiffExclude.class);

src/test/java/org/apache/commons/lang3/builder/ReflectionDiffBuilderTest.java

@@ -18,6 +18,7 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import java.math.BigDecimal;
 import java.math.BigInteger;
@@ -217,6 +218,11 @@ void testGetExcludeFieldNamesWithNullValuesInExcludedFieldNamesCtor() {
         assertNotNull(reflectionDiffBuilder.build());
     }
 
+    @Test
+    void testNoDiffBuilderSet() {
+        assertThrows(NullPointerException.class, () -> ReflectionDiffBuilder.<TypeTestClass>builder().build());
+    }
+
     @Test
     void testNoDifferences() {
         final TypeTestClass firstObject = new TypeTestClass();