Re: How to let the methods of a class only can be invoked by a special package(the class not in the package)?

Wed, 23 Jan 2008 19:52:43 -0800 (PST)
On Jan 23, 12:03 am, Andreas Leitgeb <>
wrote: <> wrote:

On Jan 22, 12:51 pm, Patricia Shanahan <> wrote: wrote:

There is a class A in package XX.ZZ.GG , and A has a static method
A.GetInstance(). There are 3 classes B, C, D in package XX.ZZ .
How can I make the A.GetInstance() only can be invoked by the B, C and

There are really untidy things you could do at run time to get a stack
trace and check that the caller is one of the specified method.

However, it would be much better to reorganize the packaging.


Unfortunately I have no right to reorganize the packaging, and I don't
known how to get a stack in the JVM with Ver 1.3 .

You could throw an exception, catch it immediately, and see what you
can read from the exception's printStackTrace(), by passing it your
own PrintWriter (or PrintStream), wrapped around some ByteArrayOutputStream.

I just tried it with an (admittedly newer-than-1.3) java:
class X {
  public static void main(String[] args) { foo(); }
  public static int foo() {
    try {
       throw new Exception("foo");
    } catch (Exception e) {
    return 0;

Try, if that also works with java-1.3, in that it also
writes the "outer"-levels. To implement this in to-be-
protected code, You'd of course not print to stdout, but
instead to a bytearray.
Happy parsing that automatically. :-)

... But then, again, it's quite an unusual wish, what you made.

Thanks for all of you. You let me to find the limitation of my design.
So I change it.

I changed my design:

1 Add a protect method GetInstance() in Class B;
2 Add a class E which is extends from B in package XX.ZZ.GG. Create a
protected method GetInstance() which has the same function of
A.GetInstance() in class E. Remove the Method A.GetInstance().
3 Add a static member 'B e ' withe the default access right in Class
B, construct 'e'in the static block of B as 'E':
           static{ e = new E; }

In this design B,C and D can invoke B.e.GetInstance() which is
E.GetInstance(), any other classes that is not in package XX.ZZ (and
also not in package XX.ZZ.GG) can't invoke the E.GetInstance().

Is my design OK ?

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