Code cleanup (#1461)

* Code cleanup

* Fix flux tests

* Fix checkstyle errors

* Fix compile error

iterator/README.md

@@ -36,7 +36,7 @@ The main class in our example is the treasure chest that contains items.
 ```java
 public class TreasureChest {
 
-  private List<Item> items;
+  private final List<Item> items;
 
   public TreasureChest() {
     items = List.of(
@@ -64,7 +64,7 @@ public class TreasureChest {
 public class Item {
 
   private ItemType type;
-  private String name;
+  private final String name;
 
   public Item(ItemType type, String name) {
     this.setType(type);

iterator/src/main/java/com/iluwatar/iterator/bst/BstIterator.java

@@ -36,7 +36,7 @@ import java.util.NoSuchElementException;
  */
 public class BstIterator<T extends Comparable<T>> implements Iterator<TreeNode<T>> {
 
-  private ArrayDeque<TreeNode<T>> pathStack;
+  private final ArrayDeque<TreeNode<T>> pathStack;
 
   public BstIterator(TreeNode<T> root) {
     pathStack = new ArrayDeque<>();

iterator/src/main/java/com/iluwatar/iterator/bst/TreeNode.java

@@ -31,7 +31,7 @@ package com.iluwatar.iterator.bst;
  */
 public class TreeNode<T extends Comparable<T>> {
 
-  private T val;
+  private final T val;
   private TreeNode<T> left;
   private TreeNode<T> right;
 

iterator/src/main/java/com/iluwatar/iterator/list/Item.java

@@ -29,7 +29,7 @@ package com.iluwatar.iterator.list;
 public class Item {
 
   private ItemType type;
-  private String name;
+  private final String name;
 
   public Item(ItemType type, String name) {
     this.setType(type);

iterator/src/main/java/com/iluwatar/iterator/list/TreasureChest.java

@@ -32,7 +32,7 @@ import java.util.List;
  */
 public class TreasureChest {
 
-  private List<Item> items;
+  private final List<Item> items;
 
   /**
    * Constructor.

iterator/src/main/java/com/iluwatar/iterator/list/TreasureChestItemIterator.java

@@ -30,9 +30,9 @@ import com.iluwatar.iterator.Iterator;
  */
 public class TreasureChestItemIterator implements Iterator<Item> {
 
-  private TreasureChest chest;
+  private final TreasureChest chest;
   private int idx;
-  private ItemType type;
+  private final ItemType type;
 
   /**
    * Constructor.