如何密切监视java.util.map以进行某些插入

I have a problem debugging someone else's Java code in Eclipse and I have narrowed the problem down to a certain entry in a java.util.Map. At some stage, a certain key is put into the map, which is causing the problem. I have already checked all "put()" and "putAll()" calls to this map object, but haven't found the location at which the erroneous entry is created. I have a problem debugging someone else's Java