Question on HF Servlets & JSP 2nd - The beer expert under Java 5

[Ellery]

Dear all

I am now reading the book of HF Servlet & JSP 2nd and found the following code:

package com.example.web;
 
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import com.example.model.*;
 
public class BeerSelect extends HttpServlet{

public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException{

String c = request.getParameter("color");
BeerExpert be = new BeerExpert();
//@SuppressWarnings("unchecked")
List<String> result = be.getBrands(c);

response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("Beer Selection Advice<br/>");

Iterator<String> it = result.iterator();
while(it.hasNext()){
out.print("<br/>try: " + it.next());
}
}
}

And the BeerExpert class:

package com.example.model;
import java.util.*;
 
public class BeerExpert{
public List getBrands(String color){
List<String> brands = new ArrayList<String>();
if(color.equals("amber")){
brands.add("Jack Amber");
brands.add("Red Moose");
}else{
brands.add("Jail Pale Ale");
brands.add("Gout Stout");
}
return(brands);
}
}

Well, the question is that, BeerSelect.java cannot be compiled with the following well-know warning:

javac -classpath /usr/local/apache-tomcat/lib/servlet-api.jar:classes:. -d classes src/com/example/web/BeerSelect.java -Xlint:unchecked
src/com/example/web/BeerSelect.java:16: warning: [unchecked] unchecked conversion
found   : java.util.List
required: java.util.List<java.lang.String>
List<String> result = be.getBrands(c);
                                                  ^
1 warning

Actually I know that, when I use the @SuppressWarnings("unchecked") statement above the "List<String> result = be.getBrands(c);", the code can be compiled nicely. However, I don't want to avoid that everytime when I meet this error. But the question is : how can I change to have it compiled?

Can anyone please help me to solve this problem?

Thank you very much in advance for all your help.

[Vijitha Kumara]

Your getBrands method in BeerExpert class may return a List of Strings. That will solve the problem (actually that's a warning not a compiler error), though you may be able to run the code without it

public List<String> getBrands(String color){    

[Ellery]

Thank you very much, it works now!

Javaranch is really a nice place

[Bear Bibeault]

"alucard", please check your private messages for an important administrative matter.