gistfile1.java

public enum Clazzes {
    param1 ("java.lang.String"),
    param2 ("java.util.ArrayList");

    private final String clazz;
    Clazzes(String clazz) {
        this.clazz = clazz;
    }
    public Object get() throws Exception {
        return Class.forName(clazz).newInstance();
    }

    public static void main(String[] args) throws Exception {

        System.out.println(Clazzes.valueOf("param1").get().getClass().getCanonicalName());
        System.out.println(Clazzes.valueOf("param2").get().getClass().getCanonicalName());
    }
}