Question

two package:
a.sub.ClassA,
b.ClassB;

package a and package b are at the same level in my project.

If I want to use ClassB in ClassA, I wrote import b.* in ClassA, why does it can’t be compiled?

This is my code:
bussinessLogicService/MemberBLService.java

package bussinessLogicService;
import java.util.ArrayList;
import po.*;

public interface MemberBLService {
    public String getMemberName();
    public String getMemberID();
    //some methods more
}

busssinessService/MemberService.java

package bussinessLogic.controller;

import java.util.*;
import bussinessLogicService.MemberBLService;

public class MemberBLService_Stub{


}

Here is the problem:

Answer 1

There are a couple of reasons for why it could fail. Make sure that

1. file ClassA.java is located in folder ./a/sub and file ClassB.java is located in folder ./b
2. the first line in ClassA.java is package a.sub;, the first line in the other file is package b;
3. both classes are declared as public (like: public class ClassA)
4. the import statement is written like: import b.*; (import b.ClassB; should work too)
5. ClassB gets compiled before ClassA (compiler needs to see ./b/ClassB.class)