Thanks, but that just turned 1 error into 20 (literally!). I'll try
again, extracting it out of Eclipse and into a simple command line/javac
test. Here are two trivial classes:

// FooClass.java
import java.util.*;

public class FooClass extends TreeMap {
    public void add(PTX ptx) {
    this.put(ptx.getID().toString(), ptx);
    }
}

// PTX.java
import java.util.*;

public class PTX extends TreeSet {
    public String getID() {
    return "XXX";
    }
}

using 1.5.0_05 they compile with a warning using javac:

% javac FooClass.java
Note: FooClass.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

% javac -Xlint:unchecked FooClass.java
FooClass.java:5: warning: [unchecked] unchecked call to put(K,V) as a
member of the raw type java.util.TreeMap
    this.put(ptx.getID().toString(), ptx);

OK, so this is similar to what Eclipse says. Upon adding the parameters
as suggested I get3 hard errors:

% javac -Xlint:unchecked FooClass.java
FooClass.java:3: cannot find symbol
symbol: class K
public class FooClass<String, PTX> extends TreeMap<K, V> {
                                                   ^
FooClass.java:3: cannot find symbol
symbol: class V
public class FooClass<String, PTX> extends TreeMap<K, V> {
                                                      ^
FooClass.java:5: cannot find symbol
symbol  : method getID()
location: class java.lang.Object
    this.put(ptx.getID().toString(), ptx);

I think you mean:

public class FooClass extends TreeMap<String, PTX> {
 public void add(PTX ptx) {
   this.put(ptx.getID().toString(), ptx);
 }
}

To the OP:

   In this case, FooClass is not generic at all. That is, the client CANNOT
specify that "This is a FooClass of Buttons". They deal with FooClasses,
which are hardcoded to deal with Strings and PTXes. So FooClass itself isn't
generic.

   However, under the covers, FooClass uses TreeMap, and TreeMap *IS*
generic. In this case, you're using TreeMaps mapping strings to PTXes, but
someone else might use the exact same TreeMap to map Integers to Users, for
example.

   That's why you need to use type name arguments for TreeMap, but not for
FooClass.

   - Oliver

I believe that should be:

public class FooClass<String, PTX> extends TreeMap<String, PTX>