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I've learn C++ for some time, however there is always this question which puzzles me (for years). In school, our lecturers like to declare class variables as private. In order to access it, we have to declare an accessor to access it. Sometimes we even have to make the different classes become "friends" into order to access its elements. My question is: Why make it so troublesome? What is the true rationale behind all the private and protected stuff when we can just make our life as a programmer easier by using public for everything? I was thinking, once the code gets compiled, the end user

Possible? Can you change the access of anything to anything else? No, you can hide a public member with a private method in a subclass, but you cannot override a public member with a private one in a subclass. And, in actually, it's not just a public/private thing, this applies to narrowing the access in general. Revised : By hiding with a more restrictive access - in this case private access - you will still see the base class member from a base-class or sub-class reference, but it would defer to the new method when available from the new access level. So in general, when you hide, the hide

I happen to come across a Java code at my work place. Here's the scenario: There are 2 classes - ClassA and ClassB . ClassA has nothing except 4 public static final string values inside it. Its purpose is to use those values like ClassA.variable (don't ask me why, it's not my code). ClassB imports ClassA . I edited the string values in ClassA and compiled it. When I ran ClassB I could see it was using the old values - not the new values. I had to recompile ClassB to make it use new values from ClassA ! (I had to recompile other classes that imports ClassA !) Is this just because of JDK 1.6 or

I found this sample code to get all local IP addresses, but I don't find an easy solution to get the public IP. A legacy class from Apple allowed to do that ... but it's legacy ... I have used ALSystemUtilities in the past. You basically have to make a call externally to find this out. + (NSString *)externalIPAddress { // Check if we have an internet connection then try to get the External IP Address if (![self connectedViaWiFi] && ![self connectedVia3G]) { // Not connected to anything, return nil return nil; } // Get the external IP Address based on dynsns.org NSError *error = nil; NSString

If I have two classes for example as follows: class A {...} class B {...} If I want to make class A public to class B , do I just make the members of class A public or I can just use public class A {...} ? Is there a way to tell class B for example that only class A is public for you? In other words, can I make public classes to A protected or private to others? Or, this is just a matter of deriving a class (inheritance)? Thanks. There's a substantial difference between making the class public and making its contents public. If you define your class in an include file (.h file) then you are

I am trying to create a Android Application which uses 3 spinners. I keep getting this error and I can't figure out how to fix it. This class should be public (android.support.v7.internal.widget.ActionBarView.HomeView) On the "v7-appcompat" library: preferences -> Android Lint Preferences Search for "Instantiatable" and set to Warning. If you are using Eclipse: Project > Clean > OK Or Try: Preferences -> Android Lint Preferences Search for Instantiatable and set as Warning . http://developer.android.com/tools/debugging/improving-w-lint.html This worked for me. Go to appcompat_v7 library ->