Your example isn't that hard too cook up... Using reflection you can query the object quite easily. This example is way off from being fool-proof (null checks for example...), but it gives a general idea. The getter for the fieldname should be written in the Java spec case, so a fieldname town, would have a getter getTown(). Simple as that :)



I had 5 minutes to spare so there you go: (Obviously the main() method, and the TestObject are there for errmmm, well, testing purposes...)

import java.util.*;
import java.lang.reflect.Method;
import java.lang.reflect.InvocationTargetException;

public class MapUtil {

    public static Map generateMap( Collection c, String fieldname) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException {
        Map result = new HashMap();
        for (Object o : c) {
            Method m = o.getClass().getMethod( "get" + String.valueOf(fieldname.charAt( 0)).toUpperCase() + fieldname.substring( 1) , new Class[0]);
            result.put( m.invoke(o,null), o );
        }

        return result;
    }

    public static void main( String[] args ) {
        List l = new ArrayList( );
        l.add( new TestObject( "first") );
        l.add( new TestObject( "second") );
        l.add( new TestObject( "third") );
        l.add( new TestObject( "fourth") );

        try {
            Map m = generateMap( l, "name");
            for ( Iterator i = m.entrySet().iterator(); i.hasNext(); ) {
                Map.Entry entry  = (Map.Entry) i.next();
                System.out.println( "key: " + entry.getKey() + ", value: " + entry.getValue() );
            }

        }
        catch ( NoSuchMethodException e ) {
            e.printStackTrace();
        }
        catch ( IllegalAccessException e ) {
            e.printStackTrace();
        }
        catch ( InvocationTargetException e ) {
            e.printStackTrace();
        }
    }


}
class TestObject {
    private String name;

    public TestObject( String name ) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public String toString() {
        final StringBuffer sb = new StringBuffer();
        sb.append( "TestObject" );
        sb.append( "{name='" ).append( name ).append( '\'' );
        sb.append( '}' );
        return sb.toString();
    }
}