Compile Xlint Errors

[B Crosthwaite]

Hi Guys,

I am in the process of following a tutorial from the head first JSP & servlets book and i have got stuck. Hopefully someone will be able to help me.

I have copied this code from the book

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

When i come to compile the code i get this message in the terminal

Note: src/com/example/model/BeerExpert.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

After i recompile with -Xlint i get these messages

src/com/example/model/BeerExpert.java:9: warning: [unchecked] unchecked call to add(E) as a member of the raw type java.util.List
brands.add("Jack Amber");
                                  ^
src/com/example/model/BeerExpert.java:10: warning: [unchecked] unchecked call to add(E) as a member of the raw type java.util.List
brands.add("Red Moose");
                                  ^
src/com/example/model/BeerExpert.java:13: warning: [unchecked] unchecked call to add(E) as a member of the raw type java.util.List
brands.add("Jail Pale Ale");
                                  ^
src/com/example/model/BeerExpert.java:14: warning: [unchecked] unchecked call to add(E) as a member of the raw type java.util.List
brands.add("Gout Stout");
                                  ^
4 warnings

Does anyone have any idea where i am going wrong?

Thanks,
-Ben

[Rob Spoor]

They aren't errors but warnings.

If you read this part of the Java Tutorial I'm sure you'll get a better understanding.

[Reinhard Horn]

Hi Ben,

replace

public List getBrands(String color) {

with

public List<String> getBrands(String color) {

and

List brands = new ArrayList();

with

List<String> brands = new ArrayList<String>();

and your warnings will vanish. The problem has to do with generics, which are introduced
since Java Version 1.5

Kind regards

[B Crosthwaite]

Thank you worked like a charm.

-Ben