[COLLECTIONS-265] TreeBag allows uncomparable item to be added, breaking toString

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.2
• Fix Version/s: 4.0-alpha1, 4.0
• Component/s: Bag
• Assignee: Unassigned
• Reporter: David Saff
• Created: 10/Sep/07 19:38
• Updated: 09/Nov/14 14:31
• Resolved: 28/Feb/13 20:04

Description

The following code throws an exception not when the Object is added, but when toString is called:

TreeBag bag = new TreeBag();
bag.add(new Object());
bag.toString();

Trace:

java.lang.ClassCastException: java.lang.Object
at java.util.TreeMap.compare(TreeMap.java:1093)
at java.util.TreeMap.getEntry(TreeMap.java:347)
at java.util.TreeMap.get(TreeMap.java:265)
at org.apache.commons.collections.bag.AbstractMapBag.getCount(AbstractMapBag.java:116)
at org.apache.commons.collections.bag.AbstractMapBag.toString(AbstractMapBag.java:581)
[...]

In a client program, toString should never throw an exception--it makes debugging much harder, for one thing. I believe that TreeBag should defend against the addition of uncomparable objects, so that toString will never throw an exception.