Accessing inner Classes.. how?

I'm reading the Java API and there is an Interface class named DocumentEvent that has an inner class named DocumentEvent.ElementChange..
Since all is well with adding a DocumentListener (as per the API) for DocumentEvents, how is it possible to access the inner class' method? Do I need to implement another interface i.e. ElementChange and then write out all the methods?? What I really want is to use a method from DocumentEvent - getChange( Element elem) but this one relates to the inner class somehow.. can anyone answer this?
Thanks so much!!!

For example, in the caller
A a = new A();
(a.new B()).mm();for the method mm() in the inner class B of the class A.
class A{
class B{
void mm(){
System.out.println(Integer.MIN_VALUE);
}

Similar Messages

Accessing inner classes

I am making a simple drawing program where the user can draw with the mouse on a jpanel.
i have my program structure with one big class and two inner classes
the first inner class creates the panel you can draw on and the mouselistener events to allow a user to draw.
the second class creates another jpanel that allows you to make a color with the three properties red,green and blue. it also has two buttons. one to set the forground(the color you will draw with) and the other to set the background.
I can get the forground one to work because i set the color created to a varible and sense there are mouse listners everytime the mouse listener executes it can grab that varible and set the color of the line be drawn.
my problem is with the background, i can't figure out how to access my first inner class from my second inner class to change the panels background to corspond with the user.
is there some listener i can apply or a way to change the properties of one inner classes objects from another inner class???
please help

I dont knoew if I understand your problem exactly- but if you are wanting to access the first inner class from the second inner class- you can go through the outer class like so:
public class InnerOuter {
public InnerOuter() {
public void test(String s) {
    Inner i = new Inner();
    i.setBackground(s);
class Inner{
    public String B="inner";
    public void setBackground(String s){
      //do something
class Inner2{
    public String C="inner2";
    public void setBack2(){
      InnerOuter.this.test("red");
public static void main(String[] args) {
    InnerOuter innerOuter1 = new InnerOuter();

In onLoad JavaScript, I'm getting "Error: Permission denied to access property 'classes'" when I access Components.classes; how do I enable that permission?

I need to emulate several ActiveX functions in my client's web application. I have located several Mozilla web pages that describe how to do the things I need, and I have attempted to implement those instructions. However, I can't seem to get past the first line of code. In my web page, I am calling a JavaScript function using the onLoad attribute of the <body> tag. I am using the Navigator object to determine that the browser is Firefox. I then attempt to access the extension classes using the following code on lines 51 and 52 of the Download.js file:
var C = Components;
var CC = C.classes;
The Web Console gives me these two messages:
[13:51:55.621] The Components object is deprecated. It will soon be removed. @ http://distribution:781/NewDDI/DownLoad.js:51
[13:51:55.621] Error: Permission denied to access property 'classes' @ http://distribution:781/NewDDI/DownLoad.js:52
How do I enable adequate permission to be able to access the Components classes?

I think Components is available only in extensions (or otherwise privileged code) and not in ordinary web pages.

Outer Class Accessing Inner Classes Variables

Hi Everyone,
Should an outer class directly access the private member variables of its inner class? Or should it get their values by calling an appropriate 'getXXX()' method?
Just wondering.
Thx.

If the outer class trys to access the variable that is declared in the inner class with in a class and outside the method, then it can access in the following example
class outer
     private int x=10;
     class inner
          int y=20;
     public void getOutput()
          inner in=new inner();
          System.out.println("The value of y is" +in.y);
     public static void main(String args[])
          outer out=new outer();
          out.getOutput();
};

Your Opinions: Inner Classes Need static Members

Hi All,
I want to solicit opinions for a minor change to the way inner classes work. I submitted this as an RFE to Sun and they rejected it, really without giving a reason. I'd like to know your opinions. If there is strong support I will repost the RFE.
As you probably know, inner classes cannot have static members. The following generates a compiler error:import java.util.*;
public class MyClass {
   class MyInnerClass {
      // Next line causes compiler error...
      static Map m = new HashMap();
}In order to get around this you have to make the Map variable a static member of the containing class:import java.util.*;
public class MyClass {
   static Map m = new HashMap(); // so much for encapsulation...
   class MyInnerClass {
}I am suggesting that inner class be allowed to contain static members. Here's my reasoning...please comment:
There are times when members (i.e., fields and methods) rightfully belong to the class as a whole, not to any particular instance of a class. I'm sure we've all found times when it was necessary to have static members in our classes. The same issues that necessitated using static members in top-level classes make them desirable for inner classes as well.
Designing a class as an inner class is a step toward encapsulation. By forcing static members that logically belong in an inner class to be declared in the containing class is to crack the encapsulation, IMHO.
Even though a containing class has access to all of an inner class' members (including private members) and vice versa, I think the notion of inner static members still is more OO-ish.
What are your opinions? Would allowing inner classes to contain static members make Java more object oriented? I think it would.
Technically, I don't think there's any reason this cannot work since the JVM has no notion of inner classes, per se.
What do you think?

an inner class is effectively a non static instance
variable of its enclosing class. Instance member, but not a variable. it's a class, a type, not a variable.
>
I think the problem here is that making a field static
means more than just that that field and its value are
common to every instance of the class. It means that
the value is valid without an instantiation of that
class.
Since the class itself must be instantiated (it is
not static), What do you mean, excatly, by "_must_ be instantiated"? You are not ever "required" to instantiate anything unless you want to use it.
you can't have static member data inside it. I don't see how this follows from the previous part of the statement.
How would you reference the static member data of
the inner class? You would have to specify an
instance of the inner class, and since this breaks
the meaning of static, you can't have static members
in an inner class.How about outerObj.InnerClass.staticMember The syntax is well defined. The question at hand is, do we really want to allow this? The syntax to do this should only be an issue after that question has been answered in the affirmative. The people at Sun have decided not to allow it, so for now, syntax is a non-issue.
>
if you wanted a static member in an inner class you
could put it in a super class of the inner class...Or in the enclosing class, as suggested in the orginal post.

Doubt in Inner class

hi ,
i have a doubt. How we can access a Inner class name by the outer class name using the Dot(.) operator .
For example if we want to refer to the Inner class in some other class
then we must say "OuterClass.InnerClass".
This type of syntex is ment for the static methods in a class.
Thus can we assume that Inner class is also a type of static member.
If not then please explain the syntex.
i am also not getting the way we create object of the Inner class object in some other class . (i mean to say the logic behind the syntex)
i.e
OuterClass Ob1=new OuterClass();
OuterClass.InnerClass InnOb=Ob1.new InnerClass();
Cna any one please help me out.
Regards
Arunabh

Hi,
Inner classes are used to create some functionality in terms of OO way. Like you want to have event handling which will work only for designated GUI classes, then we can make use of Innner class.
Within a outer classes we do not require any reference of outer object BUT, if you want to access Inner class object outside the class then only we need a reference of Outer object so that we instantitate Inner class object.
thanks,
Sandeep

How to access var in outter class inside inner class

I've problem with this, how to access var number1 and number2 at outter class inside inner class? what statement do i have to use to access it ? i tried with " int number1 = Kalkulator1.this.number1; " but there no value at class option var y when the program was running...
import java.io.*;
public class Kalkulator1{
int number1,number2,x;
/* The short way to create instance object for input console*/
private static BufferedReader stdin =
new BufferedReader( new InputStreamReader( System.in ) );
public static void main(String[] args)throws IOException {
System.out.println("---------------------------------------");
System.out.println("Kalkulator Sayur by Cumi ");
System.out.println("---------------------------------------");
System.out.println("Tentukan jenis operasi bilangan [0-4] ");
System.out.println(" 1. Penjumlahan ");
System.out.println(" 2. Pengurangan ");
System.out.println(" 3. Perkalian ");
System.out.println(" 4. Pembagian ");
System.out.println("---------------------------------------");
System.out.print(" Masukan jenis operasi : ");
String ops = stdin.readLine();
     int numberops = Integer.parseInt( ops );
System.out.print("Masukan Bilangan ke-1 : ");
String input1 = stdin.readLine();
int number1 = Integer.parseInt( input1 );
System.out.print("Masukan Bilangan ke-2 : ");
String input2 = stdin.readLine();
int number2 = Integer.parseInt( input2 );
     Kalkulator1 op = new Kalkulator1();
Kalkulator1.option b = op.new option();
     b.pilihan(numberops);
System.out.println("Bilangan yang dimasukkan adalah = " + number1 +" dan "+ number2 );
class option{
int x,y;
     int number1 = Kalkulator1.this.number1;
     int number2 = Kalkulator1.this.number2;
void pilihan(int x) {
if (x == 1)
{System.out.println("Operasi yang digunakan adalah Penjumlahan");
        int y = (number1+number2);
        System.out.println("Hasil dari operasi adalah = " + y);}
else
{if (x == 2) {System.out.println("Operasi yang digunakan adalah Pengurangan");
         int y = (number1-number2);
         System.out.println("Hasil dari operasi adalah = " + y);}
else
{if (x == 3) {System.out.println("Operasi yang digunakan adalah Perkalian");
         int y = (number1*number2);
         System.out.println("Hasil dari operasi adalah = " + y);}
else
{if (x == 4) {System.out.println("Operasi yang digunakan adalah Pembagian ");
         int y = (number1/number2);
         System.out.println("Hasil dari operasi adalah =" + y);}
else {System.out.println( "Operasi yang digunakan adalah Pembagian ");
}

Delete the variables number1 and number2 from your inner class. Your inner class can access the variables in the outer class directly. Unless you need the inner and outer class variables to hold different values then you can give them different names.
In future place code tags around your code to make it retain formatting. Highlight code and click code button.

How to access private method of an inner class using reflection.

Can somebody tell me that how can i access private method of an inner class using reflection.
There is a scenario like
class A
class B
private fun() {
now i want to use method fun() of an inner class inside third class i.e "class c".
Can i use reflection in someway to access this private method fun() in class c.

I suppose for unit tests, there could be cases when you need to access private methods that you don't want your real code to access.
Reflection with inner classes can be tricky. I tried getting the constructor, but it kept failing until I saw that even though the default constructor is a no-arg, for inner classes that aren't static, apparently the constructor for the inner class itself takes an instance of the outer class as a param.
So here's what it looks like:
        //list of inner classes, if any
        Class[] classlist = A.class.getDeclaredClasses();
        A outer = new A();
        try {
            for (int i =0; i < classlist.length; i++){
                if (! classlist.getSimpleName().equals("B")){
//skip other classes
continue;
//this is what I mention above.
Constructor constr = classlist[i].getDeclaredConstructor(A.class);
constr.setAccessible(true);
Object inner = constr.newInstance(outer);
Method meth = classlist[i].getDeclaredMethod("testMethod");
meth.setAccessible(true);
//the actual method call
meth.invoke(inner);
} catch (Exception e) {
throw new RuntimeException(e);
Good luck, and if you find yourself relying on this too much, it might mean a code redesign.

Inner class inside a method - how does it access method's local variable?

hello All:
I've learnt that, an inner class, if defined inside a method, it can access the method's local variables, only when they are defined as "final".
Anyone can help explain the rationale behind it?
Thanks a lot!
Sway

fathomBoat wrote:
In java, everything is about pass-by-reference.
Wrong! Nothing in Java is ever pass-by-reference.
Java uses pass-by-value everywhere.
It makes sense to me if the reason of enforcing a variable to be "final" is to prevent it being messed up.No, the reason is that a copy is made and if the variable weren't final then it could change later on and the developer could be confused because his inner class didn't "see" that change.
The variable being final prevents that scenario.
However, if a copy of the variable is made inside the inner class, i dont see how possible it could affect variables outside of class?Such a copy is made, but the language designers wanted to hide that fact from the developer. By forcing all accessed variables to be declared final the developer has no way to realize that he's actually working on a copy.

How to access the int variable in the inner class

hi all,
i can't access the int variable in the inner class. can any one help me
int count = 0;
MouseMoveListener mouseMove = new MouseMoveListener() {
     public void mouseMove(MouseEvent e) {
          count1++;
          System.out.println(count);
};how to access count variable
thanks

for this how can i access the countIf the count variable is a local variable you can't access it from within the
inner class. Make it a member variable of the outer class instead:public class Outer {
   private int count;
   MouseMoveListener mouseMove= new MouseMoveListener() {
      public void mouseMove(MouseEvent me) {
         count++;
         System.out.println(count);
}Alternatively, if you don't need that count variable anywhere else, you
could simply make it a member variable of the inner class itself:public class Outer {
   MouseMoveListener mouseMove= new MouseMoveListener() {
      private int count;
      public void mouseMove(MouseEvent me) {
         count++;
         System.out.println(count);
}kind regards,
Jos

How to access super of enclosing class from inner class?

Hello,
I'd like to access Base.foo() from inner class in overridden Improved.foo(), but seem unable:
public class InnerSuper {
     public static class Base {
          protected int foo() {
               return 1;
     public static class Improved extends Base {
          @Override
          protected int foo() {
               return Integer.parseInt(new Object () {
                    public String toString() {
                         return "1"+foo() ;
               }.toString());
     public static void main(String[] args) {
          System.out.println(new Improved().foo());
}The code above does not work, as it recursively calls Improved.foo() where I'd like it to call Base.foo(). What syntax construct should I use? Improved.this would be the same thing, Improved.super does not exist.
I came up with a work around: adding a method baseFoo() to Improved and call that in the inner class:
   int baseFoo() {
      return super.foo();
   } but remain wondering if that is necessary?

Indeed, Improved.super.foo() is allowed. My Eclipse syntax highlighting seems to have the same opinion as you: "are you sure you want to write that kind of code?" and leaves the read underlining for a syntax error on for just a second longer.
This is where I am now:
     public static class DeferredExecSubroutineCall extends SubroutineCall {
          RelayExecutor relay;
          public DeferredExecSubroutineCall(RelayExecutor relay) {
               this.relay = relay;
          @Override
          protected String execute(final IFDSOC fd, final String commandText) {
               Future<String> f = relay.submit(new Callable<String>() {
                    @Override
                    public String call() throws Exception {
                         return DeferredExecSubroutineCall.super.execute(fd, commandText);
               try {
                    return f.get();
               } catch (InterruptedException e) {
                    throw new RuntimeException(e);
               } catch (ExecutionException e) {
                    if (e.getCause() instanceof RuntimeException) {
                         throw (RuntimeException) e.getCause();
                    } else {
                         throw new RuntimeException(e.getCause());
     }which is my current effort of adding concurrency to an existing project. I find it quite elegant but I am interested to hear from you...

Accessing method in an inner class

I have a class, which has an Inner Class, which is an extension of AbstractTableModel. The extended TableModel class has a new method, so it looks something like this;
public class TheOuterClass
    JTable aTable
    TableModel theTableModel
    public initTable
         theTableModel = new MyTableModel();
     public TableModel getModel()
         return theTableModel;
     private class MyTableModel extends AbstractTableModel
            public void myTableModelMethod()
}So, the idea here is that I have a class that has a table referenced by 'aTable', which uses MyTableModel as the class for it's table model. I have only implemented the basics here. The class also has a method called getModel(), so from a reference to 'TheOuterClass', I can access the table model.
Now, say I have a reference to TheOuterClass called toc, and I want to access my new method in the table model;
toc.getModel().myTableModelMethod()The above won't work, because getModel() returns a type of TableModel.
My question then is how do I cast this to the correct type, so I can access the method 'myTableMethod()'?
Is for example, the following a legal possibility, because I cannot seem to make it work;
(toc.getModel().getClass())(toc.getModel()).myTableMethod();The quick fix, I guess is to correct getModel in TheOuterClass, so it returns the correct type, but I am hoping to not do this. (This is part of a larger piece of code obviously, and TheOuterClass is in reality a bean, and I don't wnat to disturb anymore than I have to).
Any suggestions / ideas would be gratefully appreciated

You are of course both correct, the class is private, should have spotted that! Doh. Also correct in that this is 'not the most elegant design', but you know the way it is you have to work with what you are given.
So, I changed the class to public....
What I had hoped is that the following would work
((toc.getModel().getClass())(toc.getModel())).myTableMethod()get a reference to the table model
(toc.getModel())cast it to the correct type (not sure if this is a valid way to cast??)
((toc.getModel().getClass())(toc.getModel()))then call the method.
This does not compile, it complains about a missing ')', and I'm sure they are all there. My question here then is, Is this a valid way to cast, now that the inner class is public?
As to why I want to do this, then some explanation is required;
The table model holds a Vector with all the data in it, some which is not actually in the table (it was originally written this way). My additional method myTableMethod() is intended to help access the data that is not shown in the table.
Coming back to kajbj's point of creating an interface, I presume what is being suggested is that I create a public interface with the myTableMethod() in it, and make myTableModel implement this interface. Since the interface is public, then I can cast to that. Is this what you meant?
Thanks for your help so far

Inner Classes Changing Access Rights Of Parent Members

I read that if you access a parent class's private memebers or methods from within an inner class, those members of methods will automatically and silently be converted to having package access. This seems dangerous and I'd like to know how I could design around it.
Here is my current dilemma. I have an EventHandler class whose handleEvent() method changes with the object's state. I've implemented this using the Strategy Pattern, where the Strategy objects are inner classes of EventHandler. The problem is that these Strategy objects need access to certain private members and methods of their parent. There is no reason, however, to give package access to these members and methods. What can I do? Or does this suggest that I need a design change? Other than this issue, though, I'm quite happy with the design.
Thanks for any thoughts,
John

When inner classes access private fields or methods, the compiler generates new package-private methods
with names like "access$000":
import java.lang.reflect.*;
public class X {
    private void x() {}
    class Y {
        public void y() {
            x();
    public static void main(String[] args) {
        Method[] methods = X.class.getDeclaredMethods();
        for(int i=0; i<methods.length; ++i)
            System.out.println(methods.getName());
So it's not correct that the access to fields or methods is changed, just that additional methods are added.
Unless you're in the habit of writing method names that contain '$', I think it's unlikely that you'll directly call
these new methods, and if you do, it should be easy to spot!

Accessing Enclosing Class Members From Inner Class Subclass

I have the following scenario that I cannot get to work. Notice the comments in B.doWork() for the problem code. In B.doWork(), how do I access m_strA?
* A.java
* Created on July 5, 2002, 2:20 PM
package Projects.InnerTrouble.Files;
public class A {
     public abstract class InnerA {
          public abstract void doWork ();
     public String m_strA;
     /** Creates new A */
     public A ()
               new InnerA() {
                         public void doWork ()
                                   System.out.println("A$InnerA$1's doWork() called!");
                                   m_strA = "Annonymous subclass of InnerA's doWork did this";
                    }.doWork();
     * @param args the command line arguments
     public static void main (String args[])
               A oTemp = new A();
               System.out.println(oTemp.m_strA);
               B.getB(oTemp).doWork();
               System.out.println(oTemp.m_strA);
class B extends A.InnerA {
     public B (A a)
               a.super();
     public void doWork ()
               System.out.println("B's doWork() called!");
               // How do I access m_strA within B's doWork() method? The following is what I would expect to be the answer, but it does not compile
               // A.this.m_strA = "B's doWork did this";
     private static A.InnerA sm_oInnerA;
     public static A.InnerA getB (A a)
               if (sm_oInnerA == null)
                    sm_oInnerA = new B(a);
               return (sm_oInnerA);

The whole point is that B is not an inner class of A
so it does not have access to A's member variables.
Eventhough B extends an inner class of A, that does
not make B an inner class of A. That is in the JLS,
but not so elegantly as I have put it, hehe.
If B were an innerclass of InnerA, then it would
qualify to access A's member variables.OK, I think that you are finally getting through to my thick skull on this one. Let me restate and get your check-off on my understanding of the situation.
The only classes with access to A's this reference are A and inner classes of A that are found within the definition of A. So, despite the fact that A and B are in the same package (and B should have access to A's non-private members because B and A are in the same package), and despite the fact that we would normally state that B "is a" InnerA (which is an inner class of A and would have access to a reference to the A.this reference), B is not allowed access to A.this (because B "is not really a" InnerA in the same way that the anonymous implementation of InnerA "is a" InnerA). However, nothing would prevent me from giving B access to a reference of the enclosing A as long as it was done via a method of InnerA, and as long as the implementation of that method is contained in A's implementation.
Does this "access" rule realy make sense? Are you aware of the justification for this rule? Or is the justification stated in the JLS? I would think that the compiler ought to be able to figure this kind of thing out and allow it. It seems to me the fact that I defined B in the way that I did, and the fact that B "is a" InnerA, implies that I desired a fairly tight relationship to A. In fact, I desired the exact relationship that exists for the anonymous implementation of InnerA.
The following is a modified version of my original example that runs as I originally wanted it to, but works around the access rules discussed on this forum thread:
* A.java
* Created on July 5, 2002, 2:20 PM
package Projects.InnerTrouble.Files;
public class A {
     public abstract class InnerA {
          public abstract void doWork ();
          /** added to allow implementors of InnerA that are not enclosed in A's class definition to have access to the enclosing class */
          public A myEnclosingInstance ()
                    return (A.this);
     public String m_strA;
     /** Creates new A */
     public A ()
               new InnerA() {
                         public void doWork ()
                                   System.out.println("A$InnerA$1's doWork() called!");
                                   m_strA = "Annonymous subclass of InnerA's doWork did this";
                    }.doWork();
     * @param args the command line arguments
     public static void main (String args[])
               A oTemp = new A();
               System.out.println(oTemp.m_strA);
               B.getB(oTemp).doWork();
               System.out.println(oTemp.m_strA);
class B extends A.InnerA {
     public B (A a)
               a.super();
     public void doWork ()
               System.out.println("B's doWork() called!");
               // The following is what I would expect to be the answer, but it does not compile
               // A.this.m_strA = "B's doWork did this";
               // added myEnclosingInstance() to get functionality desired above
               myEnclosingInstance().m_strA = "B's doWork did this";
     private static A.InnerA sm_oInnerA;
     public static A.InnerA getB (A a)
               if (sm_oInnerA == null)
                    sm_oInnerA = new B(a);
               return (sm_oInnerA);
}

Local variable can't be accessed from inner class ???????? Why ??????

Plesae help, help, help. I have no idea what to do with this bug.........
<code>
for ( int i = 0; i <= 2; i++ ) {
for ( int j = 0; j <= 2; j++ ) {
grids[i][j] = new MyButton ();
grids[i][j].setBorder(but);
getContentPane().add(grids[i][j]);
MyButton sub = grids[i][j];
sub.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if ( sub.getState() == 0 ) {
     sub = new MyButton( (Icon) new ImageIcon(imageFile));
     if ( imageFile.equals("cross.jpg") ) {
          sub.changeState(1);
     else {
          sub.changeState(2);
</code>
The compiler complains that "sub" is in the inner class, which is the ActionListener class, must be declared final. Please tell me what to do with it. I want to add an ActionListener to each MyButton Object in the array. Thanks ......

OK, now I changed my code to this :
for ( int i = 0; i <= 2; i++ ) {
for ( int j = 0; j <= 2; j++ ) {
    grids[i][j] = new MyButton ();
    grids[i][j].setBorder(but);
    getContentPane().add(grids[i][j]);
    grids[i][j].addActionListener(new ActionListener() {
     public void actionPerformed(ActionEvent e) {
        if ( grids[i][j].getState() == 0 ) {
           grids[i][j] = new MyButton( (Icon) new ImageIcon(imageFile));
          if ( imageFile.equals("cross.jpg") ) {
           grids[i][j].changeState(1);
          else {
          grids[i][j].changeState(2);
[/cpde]
Thanks for your advice !!!!!!
Now the compiler says that i and j are local variables accessed from inner classes, needs to be declared final. How can I solve this then ???

Accessing inner Classes.. how?

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