Using the Java Class object in boilerplate code

Question

On occasion, as much as I try to avoid it, I do generate a fair amount of boilerplate code in my programming. I've been told that the Java Class object can be used to get around boilerplate code, but I don't currently see how.

When I say boilerplate code, I'm referring to the term used to refer to text that is reused again and again, with slight modification.

public Map<String, Boolean> loadBooleanTags(File in)
{
// Code that extracts boolean tags
}

Now, suppose, you then want to load int tags, where the files are in the exact same format, but you want the data structure to be a Map<String, Integer>. The only way I can think of handling this is like so:

public Map<String, Integer> loadIntegerTags(File in)
{
// Code that extracts integer tags
}

Essentially, I copy and past the boolean method, but I make it parse an Integer instead. What are some better ways to handle this? Ideally, I'd like to have one method that outputs a map with the correct generics.

sounds very puzzling... you do program in Java but you find yourself googling for "Java Class"? assuming it's me who is missing something, can you post a few code snippets to illustrate the problem you're dealing with? — Pavel Veller, Apr 19 '12 at 02:55
Ask whoever told you that for clarification and references. You will never find anything useful googling for "Java Class" :) — David, Apr 19 '12 at 03:35
The Class object is used to represent classes and interfaces in a running Java Application. It was added in Java 5, and I've honestly never used it too much. So, I wanted to know if it could help in boilerplate code, where boilerplate code is defined as text that is reused with slight modifications. I think I asked the wrong question. Feel free to downvote this question if you guys feel it's appropriate. — Sal, Apr 19 '12 at 03:38

score 3 · Accepted Answer · answered Apr 19 '12 at 04:57

Interesting question. First of all, Class has been around since Java 1. Second, I think this is the pattern you're looking for:

public abstract class GenericMapFactory<T>
{
    public Map<String,T> makeMap(File in) throws InstantiationException, IllegalAccessException, IOException
    {
        Map<String,T> result = new HashMap<String,T>();
        BufferedReader rdr = new BufferedReader(new FileReader(in));
        String line = null;
        while ((line=rdr.readLine()) != null)
        {
            String key  = "" /* something meaningful for your application */; 
            T      item = parse(line);
            result.put(key, item);
        }
        return result;
    }

    protected abstract T parse(String line);
}

For every variation you need you provide a specialization, for example:

public static class IntMapFactory extends GenericMapFactory<Integer>
{
    @Override
    protected Integer parse(String line)
    {
        Integer result = null; 
        // parse the line, setting the value of result
        return result;
    }
}

All the 'boilerplate' code is factored out into a generic superclass and only the type-specific code needs to be written. You use it as follows:

File in = ...
Map<String,Integer> msi = new IntMapFactory().makeMap(in);

Using the Java Class object in boilerplate code

1 Answers1