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POCreating a Generic CsvReader
 

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    <p>I'm trying to create a simple class to read a csv file and store the contents in an</p> <pre><code>ArrayList&lt;ArrayList&lt;T&gt;&gt;. </code></pre> <p>I'm creating a generic class CsvReader so that I can handle data of different types: int, double, String. If I had, say, a csv file of doubles, I was imagining I would use my class like this:</p> <pre><code>//possible method 1 CsvReader&lt;Double&gt; reader = new CsvReader&lt;Double&gt;(); ArrayList&lt;ArrayList&lt;Double&gt;&gt; contents = reader.getContents(); //possible method 2 CsvReader reader = new CsvReader(Double.class); ArrayList&lt;ArrayList&lt;Double&gt;&gt; contents = reader.getContents(); </code></pre> <p>But method 1 won't work since type erasure prevents you from writing code like</p> <pre><code>rowArrayList.add(new T(columnStringValue)); </code></pre> <p>But I can't even make the passing in a Double.class solution work. The problem is that what's really going on is that I need my class "parameterized" (in the general sense of that word, not the technical java generics sense) on a type with the following property: it has a ctor accepting a single String argument. That is, to create the row ArrayLists on, say, a Double csv file, I'd need to write:</p> <pre><code>StringTokenizer st = new StringTokenizer(line,","); ArrayList&lt;Double&gt; curRow = new ArrayList&lt;Double&gt;(); while (st.hasMoreTokens()) { curRow.add(new Double(st.nextToken()); } </code></pre> <p>Having passed in Double.class, I could get its String ctor using </p> <pre><code> Constructor ctor = c.getConstructor(new Class[] {String.class}); </code></pre> <p>but this has two problems. Most importantly, this is a general constructor that will return a type Object, which I cannot then downcast into a Double. Second, I would be missing "type" checking on the fact that I am requiring my passed in class to have a String arg constructor. </p> <p>My question is: How can I properly implement this general purpose CsvReader?</p> <p>Thanks, Jonah</p>
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