Standard Java Error Reporting
<p>I am currently working on creating a toolkit for work and I've gotten to the point where I'm wondering about error reporting.  </p>

<p>Basically all of my tools, which consist of a grouping of classes, will eventually be ran from a main method.  Many of these tools will be doing operations on file like reading them in and converting them into some sort of array of objects or writing an object array to a file in a certain format. Whenever you are dealing with data that your program didn't create there is always room for error and those errors need to be known.</p>

<p>With that said what would be a good method to document all of the errors that occur during the processing and allow them to be retrieved later?  Considering that I may want to send these error information out later I don't think that Log4J would be a good fit.  I was considering using a string builder in each of my processing classes and append all error to that builder and retrieve it later at my leisure.  I was also thinking of using some sort of arrayList or something that would hold the different types of errors but I'm a bit at a loss.  </p>

<p>Does anyone have any good methods of doing this?  </p>
