Add final modifier to private fields.

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

@@ -71,7 +71,7 @@ public class MultilineRecursiveToStringStyle extends RecursiveToStringStyle {
     private static final long serialVersionUID = 1L;
 
     /** Indenting of inner lines. */
-    private int indent = 2;
+    private final int indent = 2;
 
     /** Current indenting. */
     private int spaces = 2;

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

@@ -2367,7 +2367,7 @@ private static final class JsonToStringStyle extends ToStringStyle {
         /**
          * The summary size text start <code>'&gt;'</code>.
          */
-        private String FIELD_NAME_PREFIX = "\"";
+        private final String FIELD_NAME_PREFIX = "\"";
 
         /**
          * <p>

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

@@ -1150,8 +1150,8 @@ public void testReflectionArrays() throws Exception {
 
     static class TestObjectEqualsExclude {
         @EqualsExclude
-        private int a;
-        private int b;
+        private final int a;
+        private final int b;
 
         public TestObjectEqualsExclude(int a, int b) {
             this.a = a;

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

@@ -565,8 +565,8 @@ public void testToHashCodeEqualsHashCode() {
 
     static class TestObjectHashCodeExclude {
         @HashCodeExclude
-        private int a;
-        private int b;
+        private final int a;
+        private final int b;
 
         public TestObjectHashCodeExclude(int a, int b) {
             this.a = a;
@@ -584,9 +584,9 @@ public int getB() {
 
     static class TestObjectHashCodeExclude2 {
         @HashCodeExclude
-        private int a;
+        private final int a;
         @HashCodeExclude
-        private int b;
+        private final int b;
 
         public TestObjectHashCodeExclude2(int a, int b) {
             this.a = a;

src/test/java/org/apache/commons/lang3/time/FastDatePrinterTimeZonesTest.java

@@ -44,7 +44,7 @@ public static Collection<TimeZone> data() {
         return timeZones;
     }
 
-    private TimeZone timeZone;
+    private final TimeZone timeZone;
 
     public FastDatePrinterTimeZonesTest(TimeZone timeZone) {
         this.timeZone = timeZone;