cannot resolve class??

My code is like this:

Globals.java
--------------------------------------------------------------------------------
package topCan;

public interface Globals {
    int CARDINALITY = 2;      //cardinality of the CAN space
    int SIZE = 1000;          //number of total nodes in the CAN syste
    int LOWER_BOUND = 0;      //the lower coordinate boundary
    int UPPER_BOUND = 400;    //the upper coordinate boundary
    int NR_ALIVE_FOREVER = 6; // number of alive forever nodes that
                                     //bootstrap node keeps track of
}
--------------------------------------------------------------------------------------

Can.java
---------------------------------------------------------------------------------------
package topCan;

public class Can implements Globals {

    private int time_tick;        // the discrete timer
    private Bootstrap bstrap;     // the bootstrap node

   ................................................................
}
------------------------------------------------------------------------------------------

Bootstrap.java
-------------------------------------------------------------------------------------------
package topCan;

public class Bootstrap implements Globals {
    private int idCount;        // the counter of IDs that have been assigned
    // nodes indices ranging from 0 to NR_ALIVE_FOREVER-1 live forever

    public Bootstrap() {
      idCount = 0;              // id always starts from 1
    }
 
   ..............................................................  
 
}
-------------------------------------------------------------------------------------------------

All files are kept under the same directory. When I tried to compile Can.java, the first two errors I got were:

Can.java:9: cannot resolve symbol
symbol  : class Globals
location: class can.Can
public class Can implements Globals {
                            ^
Can.java:12: cannot resolve symbol
symbol  : class Bootstrap
location: class can.Can
    private Bootstrap bstrap;     // the bootstrap node
            ^

Anybody knows what's wrong here? thanx a lot.