How to avoid this java generics warning

Question

Take the following method, which just returns a map of fields by name:

public static < T > HashMap< String, Field > getFields( Class< T > klass ) {
    HashMap< String, Field > fields = new HashMap< String, Field >();
    for ( Field f : klass.getFields() ) {
        fields.put( f.getName(), f );
    }
    return fields;
}

The method behaves identically if you remove the generic typing in the method signature, except that you get a warning for using a raw type. I've run into other similar things, especially around reflection, where you don't necessarily have the input type. It seems like reflection is just naturally going to have problems with generics, given that reflection is built to let you work with objects when you don't know (or care about) the type.

Aside from just pasting an "@SuppressWarning" on everything, does anyone have any good ideas about more elegant way of handling reflection without being constantly scolded by generics?

Answer 1

How about this (you don't need the template parameter T , so you can skip it):

public static HashMap< String, Field > getFields2( Class<?> klass ) {
    HashMap< String, Field > fields = new HashMap< String, Field >();
    for ( Field f : klass.getFields() ) {
        fields.put( f.getName(), f );
    }
    return fields;
}

Answer 2

Effective Java, Chapter 5 (Generics) :

• Don't use raw types in new code
• Favor generic methods

So - don't remove the type parameter.