[COLLECTIONS-785] Add constant variable
diff --git a/src/main/java/org/apache/commons/collections4/CollectionUtils.java b/src/main/java/org/apache/commons/collections4/CollectionUtils.java
index 2ba465a..b5820aa 100644
--- a/src/main/java/org/apache/commons/collections4/CollectionUtils.java
+++ b/src/main/java/org/apache/commons/collections4/CollectionUtils.java
@@ -64,6 +64,33 @@
     public static final int INDEX_NOT_FOUND = -1;
 
     /**
+     * Default prefix used while converting an Iterator to its String representation.
+     *
+     * @since 4.5
+     */
+    public static final String DEFAULT_TOSTRING_PREFIX = "[";
+
+    /**
+     * Default suffix used while converting an Iterator to its String representation.
+     *
+     * @since 4.5
+     */
+    public static final String DEFAULT_TOSTRING_SUFFIX = "]";
+
+    /**
+     * A String for Colon  (":").
+     *
+     * @since 4.5
+     */
+    public static final String COLON = ":";
+    /**
+     * A String for Comma (",").
+     *
+     * @since 4.5
+     */
+    public static final String COMMA = ",";
+
+    /**
      * Helper class to easily access cardinality properties of two collections.
      * @param <O>  the element type
      */
diff --git a/src/main/java/org/apache/commons/collections4/IteratorUtils.java b/src/main/java/org/apache/commons/collections4/IteratorUtils.java
index b2c8704..d11ceef 100644
--- a/src/main/java/org/apache/commons/collections4/IteratorUtils.java
+++ b/src/main/java/org/apache/commons/collections4/IteratorUtils.java
@@ -105,17 +105,6 @@
      */
     @SuppressWarnings("rawtypes")
     public static final OrderedMapIterator EMPTY_ORDERED_MAP_ITERATOR = EmptyOrderedMapIterator.INSTANCE;
-
-    /**
-     * Default prefix used while converting an Iterator to its String representation.
-     */
-    private static final String DEFAULT_TOSTRING_PREFIX = "[";
-
-    /**
-     * Default suffix used while converting an Iterator to its String representation.
-     */
-    private static final String DEFAULT_TOSTRING_SUFFIX = "]";
-
     /**
      * Default delimiter used to delimit elements while converting an Iterator
      * to its String representation.
@@ -1405,8 +1394,8 @@
      */
     public static <E> String toString(final Iterator<E> iterator) {
         return toString(iterator, TransformerUtils.stringValueTransformer(),
-                        DEFAULT_TOSTRING_DELIMITER, DEFAULT_TOSTRING_PREFIX,
-                        DEFAULT_TOSTRING_SUFFIX);
+                        DEFAULT_TOSTRING_DELIMITER, CollectionUtils.DEFAULT_TOSTRING_PREFIX,
+                CollectionUtils.DEFAULT_TOSTRING_SUFFIX);
     }
 
     /**
@@ -1427,7 +1416,7 @@
     public static <E> String toString(final Iterator<E> iterator,
                                       final Transformer<? super E, String> transformer) {
         return toString(iterator, transformer, DEFAULT_TOSTRING_DELIMITER,
-                        DEFAULT_TOSTRING_PREFIX, DEFAULT_TOSTRING_SUFFIX);
+                CollectionUtils.DEFAULT_TOSTRING_PREFIX, CollectionUtils.DEFAULT_TOSTRING_SUFFIX);
     }
 
     /**
diff --git a/src/main/java/org/apache/commons/collections4/bag/AbstractMapBag.java b/src/main/java/org/apache/commons/collections4/bag/AbstractMapBag.java
index 114968a..4e85fb4 100644
--- a/src/main/java/org/apache/commons/collections4/bag/AbstractMapBag.java
+++ b/src/main/java/org/apache/commons/collections4/bag/AbstractMapBag.java
@@ -28,6 +28,7 @@
 import java.util.Set;
 
 import org.apache.commons.collections4.Bag;
+import org.apache.commons.collections4.CollectionUtils;
 import org.apache.commons.collections4.set.UnmodifiableSet;
 
 /**
@@ -603,19 +604,19 @@
             return "[]";
         }
         final StringBuilder buf = new StringBuilder();
-        buf.append('[');
+        buf.append(CollectionUtils.DEFAULT_TOSTRING_PREFIX);
         final Iterator<E> it = uniqueSet().iterator();
         while (it.hasNext()) {
             final Object current = it.next();
             final int count = getCount(current);
             buf.append(count);
-            buf.append(':');
+            buf.append(CollectionUtils.COLON);
             buf.append(current);
             if (it.hasNext()) {
-                buf.append(',');
+                buf.append(CollectionUtils.COMMA);
             }
         }
-        buf.append(']');
+        buf.append(CollectionUtils.DEFAULT_TOSTRING_SUFFIX);
         return buf.toString();
     }
 
diff --git a/src/main/java/org/apache/commons/collections4/list/AbstractLinkedList.java b/src/main/java/org/apache/commons/collections4/list/AbstractLinkedList.java
index ec3221f..eb8dff7 100644
--- a/src/main/java/org/apache/commons/collections4/list/AbstractLinkedList.java
+++ b/src/main/java/org/apache/commons/collections4/list/AbstractLinkedList.java
@@ -407,7 +407,7 @@
             return "[]";
         }
         final StringBuilder buf = new StringBuilder(16 * size());
-        buf.append('[');
+        buf.append(CollectionUtils.DEFAULT_TOSTRING_PREFIX);
 
         final Iterator<E> it = iterator();
         boolean hasNext = it.hasNext();
@@ -419,7 +419,7 @@
                 buf.append(", ");
             }
         }
-        buf.append(']');
+        buf.append(CollectionUtils.DEFAULT_TOSTRING_SUFFIX);
         return buf.toString();
     }
 
diff --git a/src/main/java/org/apache/commons/collections4/list/TreeList.java b/src/main/java/org/apache/commons/collections4/list/TreeList.java
index 1b8cda6..82d7ba4 100644
--- a/src/main/java/org/apache/commons/collections4/list/TreeList.java
+++ b/src/main/java/org/apache/commons/collections4/list/TreeList.java
@@ -26,6 +26,7 @@
 import java.util.NoSuchElementException;
 import java.util.Objects;
 
+import org.apache.commons.collections4.CollectionUtils;
 import org.apache.commons.collections4.OrderedIterator;
 
 /**
@@ -965,11 +966,11 @@
             return new StringBuilder()
                 .append("AVLNode(")
                 .append(relativePosition)
-                .append(',')
+                .append(CollectionUtils.COMMA)
                 .append(left != null)
-                .append(',')
+                .append(CollectionUtils.COMMA)
                 .append(value)
-                .append(',')
+                .append(CollectionUtils.COMMA)
                 .append(getRightSubTree() != null)
                 .append(", faedelung ")
                 .append(rightIsNext)
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 146968c..23e3d67 100644
--- a/src/main/java/org/apache/commons/collections4/map/AbstractHashedMap.java
+++ b/src/main/java/org/apache/commons/collections4/map/AbstractHashedMap.java
@@ -30,6 +30,7 @@
 import java.util.NoSuchElementException;
 import java.util.Set;
 
+import org.apache.commons.collections4.CollectionUtils;
 import org.apache.commons.collections4.IterableMap;
 import org.apache.commons.collections4.KeyValue;
 import org.apache.commons.collections4.MapIterator;
@@ -1404,7 +1405,7 @@
 
             hasNext = it.hasNext();
             if (hasNext) {
-                buf.append(',').append(' ');
+                buf.append(CollectionUtils.COMMA).append(' ');
             }
         }
 
diff --git a/src/main/java/org/apache/commons/collections4/map/Flat3Map.java b/src/main/java/org/apache/commons/collections4/map/Flat3Map.java
index fcaa424..4f1e657 100644
--- a/src/main/java/org/apache/commons/collections4/map/Flat3Map.java
+++ b/src/main/java/org/apache/commons/collections4/map/Flat3Map.java
@@ -28,6 +28,7 @@
 import java.util.NoSuchElementException;
 import java.util.Set;
 
+import org.apache.commons.collections4.CollectionUtils;
 import org.apache.commons.collections4.IterableMap;
 import org.apache.commons.collections4.MapIterator;
 import org.apache.commons.collections4.ResettableIterator;
@@ -1262,12 +1263,12 @@
             buf.append(key3 == this ? "(this Map)" : key3);
             buf.append('=');
             buf.append(value3 == this ? "(this Map)" : value3);
-            buf.append(',');
+            buf.append(CollectionUtils.COMMA);
         case 2:
             buf.append(key2 == this ? "(this Map)" : key2);
             buf.append('=');
             buf.append(value2 == this ? "(this Map)" : value2);
-            buf.append(',');
+            buf.append(CollectionUtils.COMMA);
         case 1:
             buf.append(key1 == this ? "(this Map)" : key1);
             buf.append('=');