How to control class file access

Question

Hi
I am developing an application in java. I am keeping only one class where the user has to enter valid password. different classes are called later as soon as the user run the application. I guss, any one can access other class even those has not main class by way of writing a new class having main method and calling all other class from that class. Will any one suggest how do I protect it?
Thanks in advance

Answer 1

package mypackage;
public class myEntryClass { // public as this class is the only one that is to be used by others
private boolean isLoggedIn; // no one can change this value except myEntryClass
public myEntryClass() {
public final void login(String user, String password) { //anyone can attempt to login - the mehod may not be overridden however by subclasses as it is final
if ( /* check if username and password is ok */ ) {
this.isLoggedIn = true;
public void callAMethod() {  // anyone logged in may do so
if (this.isLoggedIn) {
AnotherClass.aMethod();
package myPackage;
class AnotherClass {  // package/default visibility
static void aMethod() {    // package/default visibility
// do something
Hope that helps
rh