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Index › Programming Questions & Help › Syntax Questions › access modifiers
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access modifiers? (Read 442 times)
rebirth
access modifiers?
Dec 18th, 2008, 9:38am  
Code:

A a;

void setup() {
  a = new A();
  println(a.b);
}

class A{
 private int b; 
 
 A(){
  b = 5; 
 }
}


does not give an error.

Does Processing not support access modifiers? Is this a bug?
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JohnG
Re: access modifiers?
Reply #1 - Dec 18th, 2008, 12:27pm  
Everything in processing gets wrapped into another class, so your class A is actually an inner class, and I think because of that the main class has access to even private things.
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rebirth
Re: access modifiers?
Reply #2 - Dec 19th, 2008, 10:43pm  
even

Code:

A a;
B b;

void setup() {
  a = new A();
  println(a.val);
  b = new B();
}

class A{
  private int val;  

  A(){
    val = 5;
    println(val);
  }
}

class B{

  B(){
    print(a.val); 
  }
}


does not cause a problem. So as far as I can tell access modifies to nothing in processing.
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PhiLho 
Re: access modifiers?
Reply #3 - Dec 19th, 2008, 11:44pm  
Not too sure about how access is managed in inner classes, I don't feel like reading the whole Classes chapter...
But what you show is standard Java behavior:
Code:
class Test
{
  A a;
  B b;

  public static void main(String[] args)
  {
    Test tdj = new Test();
    tdj.init();
  }
 
  void init()
  {
    a = new A();
    System.out.println(a.val);
    b = new B();
  }

class A {
  private int val;

  A() {
    val = 5;
    System.out.println(val);
  }
}

class B {

  B() {
   System.out.println(a.val);
  }
}
}
compiles and runs fine in DrJava.
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« Last Edit: Dec 20th, 2008, 11:10am by PhiLho  »  
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rebirth
Re: access modifiers?
Reply #4 - Dec 20th, 2008, 12:54am  
oook...

i was not familiar with nested classes. reading...
http://java.sun.com/docs/books/tutorial/java/javaOO/nested.html
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rebirth
Re: access modifiers?
Reply #5 - Dec 20th, 2008, 12:56am  
this explains it:


A nested class is a member of its enclosing class. Non-static nested classes (inner classes) have access to other members of the enclosing class, even if they are declared private. Static nested classes do not have access to other members of the enclosing class. As a member of the OuterClass, a nested class can be declared private, public, protected, or package private. (Recall that outer classes can only be declared public or package private.)
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PhiLho 
Re: access modifiers?
Reply #6 - Dec 20th, 2008, 11:14am  
Ah, I missed it somehow. The key is indeed "Non-static nested classes (inner classes) have access to other members of the enclosing class, even if they are declared private.", which can be interpreted as: they have access to private fields of other inner classes in the same parent class.
I wouldn't dare to interpret it so far, but experiments show it is the case.
Of course, while it is good to know for expanding our knowledge, I think this is rarely used in practice (using getters for example, or other access levels like default one (package protected)).
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