Compile error saying I need to recompile servlet

[Ed Gretson]

I am trying to get my java class to compile.

My first one (the bean) compiles but the second one that calls the bean class doesnt compile:

bean class file that compiles and works:

package beans;
 
public class Customer
{
    private String _id;
    private String _firstName;
    private String _lastName;
    private String _address;
 
    public Customer(String id, String firstName, String lastName, String address)
    {
        _id = id;
        _firstName = firstName;
        _lastName = lastName;
        _address = address;
    }
 
    public String getAddress()
    {
        return _address;
    }
 
    public void setAddress(String address)
    {
        _address = address;
    }
 
    public String getFirstName()
    {
        return _firstName;
    }
 
    public void setFirstName(String firstName)
    {
        _firstName = firstName;
    }
 
    public String getLastName()
    {
        return _lastName;
    }
 
    public void setLastName(String lastName)
    {
        _lastName = lastName;
    }
 
    public String getId()
    {
        return _id;
    }
 
    public void set_id(String id)
    {
        _id = id;
    }
}

The CustomerManager Servlet that wont compile:

package beans;
 
import java.util.ArrayList;
import java.util.List;
 
public class CustomerManager
{
    public List getCustomers()
    {
        return generateCustomers();
    }
 
    private List generateCustomers()
    {
        List rv = new ArrayList();
 
        for (int i = 0; i < 10; i++)
        {
            rv.add(getCustomer(String.valueOf(i)));
        }
 
        return rv;
    }
 
    public Customer getCustomer(String id)
    {
        return new Customer(id, id + "First", "Last" + id,
            "123 Caroline Road Fooville");
    }
}

Here is my error message:

C:\Program Files\Apache Software Foundation\Tomcat 5.5\webapps\test\WEB-INF\clas
ses>javac beans\CustomerManager.java
Note: beans\CustomerManager.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

Please advise.

[ July 26, 2006: Message edited by: Ed Gretson ]
[ July 26, 2006: Message edited by: Ed Gretson ]

[Bear Bibeault]

It's compiling, that's just a warning.

[Bear Bibeault]

As this is not servlet-specific and an issue with the use of JDK 1.5 generics, this has been moved to the Java in General (intermediate) forum.

[Ed Gretson]

Thanks for your quick response.

If possible can you advise what "unchecked or unsafe operations" that are located in the CustomerManager class?

[Christian Spreiter]

as already mentioned, it's just a warning. the reason is your ArrayList and to be precise this line

rv.add(getCustomer(String.valueOf(i)));

you can add any type into this ArrayList. In your case you only want String objects in your ArrayList. Generics (as of java 1.5) solve this problem and would eliminate the warning

so instead of

List rv = new ArrayList();

use
List<String> rv = new ArrayList<String>();

this makes sure that you only add String objects to the ArrayList


hope this helps chris

[Ernest Friedman-Hill]

Originally posted by Ed Gretson:

If possible can you advise what "unchecked or unsafe operations" that are located in the CustomerManager class?

Java 5 introduced the concept of "Generics," which add "type safety" to the Collections API, among other things. The warning means, simply and completely, that you're not using this new feature.

For more info, see here.

[Ed Gretson]

thanks!

[Jesper de Jong]

Please notice the warning message that you get:

Note: beans\CustomerManager.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

Especially look at the second line. It tells you that if you want to know the details, compile your source code with the command line option -Xlint:unchecked. So, just do exactly what it says, compile your code like this:

javac -Xlint:unchecked beans\CustomerManager.java