diff --git a/src/main/java/org/apache/commons/collections4/functors/DefaultEquator.java b/src/main/java/org/apache/commons/collections4/functors/DefaultEquator.java
index 4a76fc8ee7..59a5d3feaa 100644
--- a/src/main/java/org/apache/commons/collections4/functors/DefaultEquator.java
+++ b/src/main/java/org/apache/commons/collections4/functors/DefaultEquator.java
@@ -76,6 +76,11 @@ public int hash(final T o) {
         return o == null ? HASHCODE_NULL : o.hashCode();
     }
 
+    /**
+     * Returns the singleton instance.
+     *
+     * @return the singleton instance.
+     */
     private Object readResolve() {
         return INSTANCE;
     }
diff --git a/src/main/java/org/apache/commons/collections4/functors/ExceptionClosure.java b/src/main/java/org/apache/commons/collections4/functors/ExceptionClosure.java
index ee366661ec..1b5196d256 100644
--- a/src/main/java/org/apache/commons/collections4/functors/ExceptionClosure.java
+++ b/src/main/java/org/apache/commons/collections4/functors/ExceptionClosure.java
@@ -63,6 +63,11 @@ public void execute(final E input) {
         throw new FunctorException("ExceptionClosure invoked");
     }
 
+    /**
+     * Returns the singleton instance.
+     *
+     * @return the singleton instance.
+     */
     private Object readResolve() {
         return INSTANCE;
     }
diff --git a/src/main/java/org/apache/commons/collections4/functors/ExceptionFactory.java b/src/main/java/org/apache/commons/collections4/functors/ExceptionFactory.java
index 518551bce4..04925c9a4a 100644
--- a/src/main/java/org/apache/commons/collections4/functors/ExceptionFactory.java
+++ b/src/main/java/org/apache/commons/collections4/functors/ExceptionFactory.java
@@ -63,6 +63,11 @@ public T create() {
         throw new FunctorException("ExceptionFactory invoked");
     }
 
+    /**
+     * Returns the singleton instance.
+     *
+     * @return the singleton instance.
+     */
     private Object readResolve() {
         return INSTANCE;
     }
diff --git a/src/main/java/org/apache/commons/collections4/functors/ExceptionPredicate.java b/src/main/java/org/apache/commons/collections4/functors/ExceptionPredicate.java
index 3348cbba48..bf46f60eae 100644
--- a/src/main/java/org/apache/commons/collections4/functors/ExceptionPredicate.java
+++ b/src/main/java/org/apache/commons/collections4/functors/ExceptionPredicate.java
@@ -65,6 +65,11 @@ public boolean evaluate(final T object) {
         throw new FunctorException("ExceptionPredicate invoked");
     }
 
+    /**
+     * Returns the singleton instance.
+     *
+     * @return the singleton instance.
+     */
     private Object readResolve() {
         return INSTANCE;
     }
diff --git a/src/main/java/org/apache/commons/collections4/functors/ExceptionTransformer.java b/src/main/java/org/apache/commons/collections4/functors/ExceptionTransformer.java
index 68deb5697d..b5978605ee 100644
--- a/src/main/java/org/apache/commons/collections4/functors/ExceptionTransformer.java
+++ b/src/main/java/org/apache/commons/collections4/functors/ExceptionTransformer.java
@@ -53,6 +53,11 @@ public static <I, O> Transformer<I, O> exceptionTransformer() {
     private ExceptionTransformer() {
     }
 
+    /**
+     * Returns the singleton instance.
+     *
+     * @return the singleton instance.
+     */
     private Object readResolve() {
         return INSTANCE;
     }
diff --git a/src/main/java/org/apache/commons/collections4/functors/FalsePredicate.java b/src/main/java/org/apache/commons/collections4/functors/FalsePredicate.java
index b52a0a0a0e..184234c6bf 100644
--- a/src/main/java/org/apache/commons/collections4/functors/FalsePredicate.java
+++ b/src/main/java/org/apache/commons/collections4/functors/FalsePredicate.java
@@ -63,6 +63,11 @@ public boolean evaluate(final T object) {
         return false;
     }
 
+    /**
+     * Returns the singleton instance.
+     *
+     * @return the singleton instance.
+     */
     private Object readResolve() {
         return INSTANCE;
     }
diff --git a/src/main/java/org/apache/commons/collections4/functors/NOPClosure.java b/src/main/java/org/apache/commons/collections4/functors/NOPClosure.java
index 5bfb050b40..252221e7fb 100644
--- a/src/main/java/org/apache/commons/collections4/functors/NOPClosure.java
+++ b/src/main/java/org/apache/commons/collections4/functors/NOPClosure.java
@@ -61,6 +61,11 @@ public void execute(final E input) {
         // do nothing
     }
 
+    /**
+     * Returns the singleton instance.
+     *
+     * @return the singleton instance.
+     */
     private Object readResolve() {
         return INSTANCE;
     }
diff --git a/src/main/java/org/apache/commons/collections4/functors/NOPTransformer.java b/src/main/java/org/apache/commons/collections4/functors/NOPTransformer.java
index 306792e13a..e025fc5531 100644
--- a/src/main/java/org/apache/commons/collections4/functors/NOPTransformer.java
+++ b/src/main/java/org/apache/commons/collections4/functors/NOPTransformer.java
@@ -51,6 +51,11 @@ public static <T> Transformer<T, T> nopTransformer() {
     private NOPTransformer() {
     }
 
+    /**
+     * Returns the singleton instance.
+     *
+     * @return the singleton instance.
+     */
     private Object readResolve() {
         return INSTANCE;
     }
diff --git a/src/main/java/org/apache/commons/collections4/functors/NotNullPredicate.java b/src/main/java/org/apache/commons/collections4/functors/NotNullPredicate.java
index e8ebbf604c..6913cfdb45 100644
--- a/src/main/java/org/apache/commons/collections4/functors/NotNullPredicate.java
+++ b/src/main/java/org/apache/commons/collections4/functors/NotNullPredicate.java
@@ -63,6 +63,11 @@ public boolean evaluate(final T object) {
         return object != null;
     }
 
+    /**
+     * Returns the singleton instance.
+     *
+     * @return the singleton instance.
+     */
     private Object readResolve() {
         return INSTANCE;
     }
diff --git a/src/main/java/org/apache/commons/collections4/functors/NullPredicate.java b/src/main/java/org/apache/commons/collections4/functors/NullPredicate.java
index 8aca8c8709..93820fc54f 100644
--- a/src/main/java/org/apache/commons/collections4/functors/NullPredicate.java
+++ b/src/main/java/org/apache/commons/collections4/functors/NullPredicate.java
@@ -63,6 +63,11 @@ public boolean evaluate(final T object) {
         return object == null;
     }
 
+    /**
+     * Returns the singleton instance.
+     *
+     * @return the singleton instance.
+     */
     private Object readResolve() {
         return INSTANCE;
     }
diff --git a/src/main/java/org/apache/commons/collections4/functors/StringValueTransformer.java b/src/main/java/org/apache/commons/collections4/functors/StringValueTransformer.java
index 3205edfb2a..e39caa6cff 100644
--- a/src/main/java/org/apache/commons/collections4/functors/StringValueTransformer.java
+++ b/src/main/java/org/apache/commons/collections4/functors/StringValueTransformer.java
@@ -52,6 +52,11 @@ public static <T> Transformer<T, String> stringValueTransformer() {
     private StringValueTransformer() {
     }
 
+    /**
+     * Returns the singleton instance.
+     *
+     * @return the singleton instance.
+     */
     private Object readResolve() {
         return INSTANCE;
     }
diff --git a/src/main/java/org/apache/commons/collections4/functors/TruePredicate.java b/src/main/java/org/apache/commons/collections4/functors/TruePredicate.java
index a17d319b22..ef1dd6a948 100644
--- a/src/main/java/org/apache/commons/collections4/functors/TruePredicate.java
+++ b/src/main/java/org/apache/commons/collections4/functors/TruePredicate.java
@@ -63,6 +63,11 @@ public boolean evaluate(final T object) {
         return true;
     }
 
+    /**
+     * Returns the singleton instance.
+     *
+     * @return the singleton instance.
+     */
     private Object readResolve() {
         return INSTANCE;
     }
diff --git a/src/main/java/org/apache/commons/collections4/keyvalue/AbstractKeyValue.java b/src/main/java/org/apache/commons/collections4/keyvalue/AbstractKeyValue.java
index 1a743f315c..3c13e71d0d 100644
--- a/src/main/java/org/apache/commons/collections4/keyvalue/AbstractKeyValue.java
+++ b/src/main/java/org/apache/commons/collections4/keyvalue/AbstractKeyValue.java
@@ -64,12 +64,24 @@ public V getValue() {
         return value;
     }
 
+    /**
+     * Sets the key.
+     *
+     * @param key The key.
+     * @return The previous key.
+     */
     protected K setKey(final K key) {
         final K old = this.key;
         this.key = key;
         return old;
     }
 
+    /**
+     * Sets the value.
+     *
+     * @param value The value.
+     * @return The previous value.
+     */
     protected V setValue(final V value) {
         final V old = this.value;
         this.value = value;
diff --git a/src/main/java/org/apache/commons/collections4/map/AbstractHashedMap.java b/src/main/java/org/apache/commons/collections4/map/AbstractHashedMap.java
index 8e458ad976..1e344c6908 100644
--- a/src/main/java/org/apache/commons/collections4/map/AbstractHashedMap.java
+++ b/src/main/java/org/apache/commons/collections4/map/AbstractHashedMap.java
@@ -67,9 +67,15 @@ public class AbstractHashedMap<K, V> extends AbstractMap<K, V> implements Iterab
      * @param <V> the type of the values in the map
      */
     protected static class EntrySet<K, V> extends AbstractSet<Map.Entry<K, V>> {
+
         /** The parent map */
         private final AbstractHashedMap<K, V> parent;
 
+        /**
+         * Constructs a new instance.
+         *
+         * @param parent The parent map.
+         */
         protected EntrySet(final AbstractHashedMap<K, V> parent) {
             this.parent = parent;
         }
@@ -112,6 +118,7 @@ public int size() {
             return parent.size();
         }
     }
+
     /**
      * EntrySet iterator.
      *
@@ -120,6 +127,11 @@ public int size() {
      */
     protected static class EntrySetIterator<K, V> extends HashIterator<K, V> implements Iterator<Map.Entry<K, V>> {
 
+        /**
+         * Constructs a new instance.
+         *
+         * @param parent The parent map.
+         */
         protected EntrySetIterator(final AbstractHashedMap<K, V> parent) {
             super(parent);
         }
@@ -129,6 +141,7 @@ public Map.Entry<K, V> next() {
             return super.nextEntry();
         }
     }
+
     /**
      * HashEntry used to store the data.
      * <p>
@@ -136,17 +149,22 @@ public Map.Entry<K, V> next() {
      * then you will not be able to access the protected fields.
      * The {@code entryXxx()} methods on {@code AbstractHashedMap} exist
      * to provide the necessary access.
+     * </p>
      *
      * @param <K> the type of the keys
      * @param <V> the type of the values
      */
     protected static class HashEntry<K, V> implements Map.Entry<K, V>, KeyValue<K, V> {
+
         /** The next entry in the hash chain */
         protected HashEntry<K, V> next;
+
         /** The hash code of the key */
         protected int hashCode;
+
         /** The key */
         protected Object key;
+
         /** The value */
         protected Object value;
 
@@ -206,7 +224,7 @@ public String toString() {
         }
     }
     /**
-     * Base Iterator
+     * Base Iterator.
      *
      * @param <K> the type of the keys in the map
      * @param <V> the type of the values in the map
@@ -215,12 +233,16 @@ protected abstract static class HashIterator<K, V> {
 
         /** The parent map */
         private final AbstractHashedMap<K, V> parent;
+
         /** The current index into the array of buckets */
         private int hashIndex;
+
         /** The last returned entry */
         private HashEntry<K, V> last;
+
         /** The next entry */
         private HashEntry<K, V> next;
+
         /** The modification count expected */
         private int expectedModCount;
 
@@ -285,6 +307,7 @@ public String toString() {
             return "Iterator[]";
         }
     }
+
     /**
      * MapIterator implementation.
      *
@@ -329,6 +352,7 @@ public V setValue(final V value) {
             return current.setValue(value);
         }
     }
+
     /**
      * KeySet implementation.
      *
@@ -387,6 +411,7 @@ public K next() {
             return super.nextEntry().getKey();
         }
     }
+
     /**
      * Values implementation.
      *
@@ -420,6 +445,7 @@ public int size() {
             return parent.size();
         }
     }
+
     /**
      * Values iterator.
      *
@@ -438,11 +464,22 @@ public V next() {
         }
     }
 
+    /** Exception message. */    
     protected static final String NO_NEXT_ENTRY = "No next() entry in the iteration";
+
+    /** Exception message. */    
     protected static final String NO_PREVIOUS_ENTRY = "No previous() entry in the iteration";
+
+    /** Exception message. */    
     protected static final String REMOVE_INVALID = "remove() can only be called once after next()";
+
+    /** Exception message. */    
     protected static final String GETKEY_INVALID = "getKey() can only be called after next() and before remove()";
+
+    /** Exception message. */    
     protected static final String GETVALUE_INVALID = "getValue() can only be called after next() and before remove()";
+
+    /** Exception message. */    
     protected static final String SETVALUE_INVALID = "setValue() can only be called after next() and before remove()";
 
     /** The default capacity to use */