Inner class access to outer class variables

class X extends JTextField {
int variable_a;
public X() {
setDocument(
new PlainDocument() {
//here i need access to variable_a
i don't want to make variable_a a static member though, so does anyone know how to do it?

Generally, you can reference your variable_a just as you would any other variable except if your inner class also defines a variable_a. However, to produce a reference to the enclosing outer class object you write "OuterClassName.this". So, to get to your variable I think you would write "X.this.variable_a". I hope this helps.

Similar Messages

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();
};

Inner class variable access

Hi all
If for example I pass a JButton to a method or construcrtor of another Class. Is there a way to make this JButton accessable from all other methods or subclasses in that Class?
It's something that has caused me problems in the past, I've been able to work around the problem but I think it would make life much easier if this were possible.
Thanks

Thanks for the quick response.
So you mean I can do something like:
public class MyClass
private JButton MemberButton;
public MyClass( JButton aButton )
MemberButton = aButton;
}

Accessing member variable within an anonymous inner class

I'm getting a compiler error with the following snippet which resides in a constructor (error below):
        final String fullNamesArr[] = new String[ lafsArr.length ];
        String lafNamesArr[] = new String[ lafsArr.length ];
        JMenuItem namesMenuItemArr[] = new JMenuItem[ lafsArr.length ];
        for ( int i = 0 ; i < lafsArr.length ; i++ )
            StringTokenizer tokenizer;
            fullNamesArr[ i ] = lafsArr[ i ].getClassName();
            tokenizer = new StringTokenizer( fullNamesArr[ i ] );
            while ( tokenizer.hasMoreTokens() )
                lafNamesArr[ i ] = tokenizer.nextToken( "." );
            namesMenuItemArr[ i ] = new JMenuItem( lafNamesArr[ i ] );
            lafMenu.add( namesMenuItemArr[ i ] );
            namesMenuItemArr[ i ].addActionListener(new ActionListener()
                    public final void actionPerformed(final ActionEvent e)
                        String actionCommand = e.getActionCommand();
                        int iCount = 0;
                        for ( int index = 0 ; index < fullNamesArr.length ; index++ )
                            if ( fullNamesArr[ index ].contains( actionCommand ))
                                iCount = index;
                                break;
                        System.out.println( "Setting LAF to '" +
                                            fullNamesArr[ iCount ] + "'" );
                        try
                            UIManager.setLookAndFeel( fullNamesArr[ iCount ] );
                        catch ( UnsupportedLookAndFeelException ulafe )
                            System.out.println( fullNamesArr[ iCount ] +
                                                " : Not a valid LAF class." );
                        catch ( ClassNotFoundException cnfe )
                            System.out.println( fullNamesArr[ iCount ] +
                                                " : Class not found." );
                        catch ( InstantiationException ie )
                            System.out.println( fullNamesArr[ iCount ] +
                                                " : Can't instantiate class." );
                        catch ( IllegalAccessException iae )
                            System.out.println( fullNamesArr[ iCount ] +
                                                " : Illegal access." );
DBBuilder.java:1280: cannot resolve symbol
symbol : method contains (java.lang.String)
location: class java.lang.String
if ( fullNamesArr[ index ].contains( actionCommand ))
^
1 error
BUILD FAILED
My question: Why can I access fullNamesArr in other spots in the anon-inner class,but not with the String.contains() method? BTW, the carrot is under the left bracket '['.
TIA,
Jeff

My question: Why can I access fullNamesArr in other
spots in the anon-inner class,but not with the
String.contains() method? BTW, the carrot is under
the left bracket '['.You're misinterpreting the message. The problem is not your variable fullNamesArr, but rather the method contains(java.lang.String). Since that method was only added in Java 5 (aka 1.5) you might look if you're compiling with JDK 1.4 or earlier.

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

Why only final variables can be accessed in an inner class ?

Variables declared in a method need to declared as final if they are to be accessed in an inner class which resides in that method. My question is...
1. Why should i declare them as final ? What's the reason?
2. If i declare them as final, could they be modified in inner class ? since final variables should not modify their value.

(Got an error posting this, so I hope we don't end up with two...)
But what if i want to change the final local variable within that method instead of within anonymous class.You can't. You can't change the value of a final variable.
Should i use same thing like having another local variable as part of method and initializing it with the final local variable?You could do. But as in the first example I posted you are changing the value of the nonfinal variable not the final one. Because final variables can't be changed.
If so, don't you think it is redundant to have so many local variables for so many final local variables just to change them within that method?If you are worried that a variable might be redundant, don't create it. If you must create it to meet some need then it's not redundant.
Or is there any alternate way?Any alternate way to do what?

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 ???

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.

Why Inner class cannot access static variables

Why is it that inner class can use only static final variables of the outerclass, and not ordinary static variables of the outer class. "Yes the JLS sepcifies that only final static variables can be used inside an inner class, esp a non blank final variable". But why this restriction.
Thanks.

so what are final static variables treated as if they
are not variables. So if the final static value is
not loaded when the class is loaded how will the
class know about the value.??The actual value wil be substituted for the name of a static final value at compile time. That's why you can use them in switch statements where you can't use any variable variable.
This is something to watch out for, by the way, because if you use a public static final value from one class in another the actual value will be compiled into the using class, so if you change the value where it's defined the class using it will have the old value until it's recompiled.

Local variable accessed within inner class

Hey everybody,
My program keeps telling me that it wont work because one of my methods is calling a local variable inside an inner class. Does anyone know what this means and how to fix it?
Heres the code:
public class SliderExample extends JPanel{
int value=0;
public SliderExample(int imw, int imh, Image img, BufferedImage buf, Graphics2D biCon){
super(true);
this.setLayout(new BorderLayout());
JSlider slider= new JSlider(JSlider.HORIZONTAL,0,imw,25);
slider.setMinorTickSpacing(10);
slider.setMajorTickSpacing(100);
slider.setPaintTicks(true);
slider.setPaintLabels(true);
JButton redraw= new JButton("Scroll");
redraw.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent ev){
reDraw(slider,img,buf,biCon,imw,imh);
add(slider,BorderLayout.CENTER);
add(redraw,BorderLayout.AFTER_LINE_ENDS);
public void reDraw(JSlider slid, Image im, BufferedImage bf, Graphics2D biC, int iw, int ih){
value=slid.getValue();
Graphics g= getGraphics();
g.drawImage(im,value,0,iw,ih,this);
g.drawImage(bf,value,0,iw,ih,this);
biC.drawImage(bf,value,0,iw,ih,this);
Any ideas???
THanks,
Rick

Its getting them from another class thats calling the mothod to construct the slider bar with dedraw button. Thats a pretty big class but I will post the code where I called the method:
public class Process extends JFrame implements MouseListener, MouseMotionListener{
private int [][] points;
private int [] lengths={0};
private int [] bin;
private String imstr;
private String imsav;
private int imgw=658;
private int imgh=512;
private int xArrayPos=0;
private int yArrayPos=0;
private int xpos=0;
private int ypos=0;
private int xprev;
private int yprev;
private int xadd;
private int yadd;
private String filstr;
Image image;
SimpleGUI gui;
BufferedImage buffer;
Graphics2D biContext;
Graphics2D g2;
BufferedImage last;
Graphics2D lastContext;
public Process(){
JFrame slideFrame = new JFrame("Please slide to scroll image");
slideFrame.setContentPane(new SliderExample(imgw, imgh,image,buffer,biContext));
slideFrame.pack();
slideFrame.setVisible(true);
Thats what anything having to do with that function in the other class that calls the Slider Class.
Do you know how I can fix this??
Thanks,
Rick

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.

Setting variables from inner class

I have a GUI that takes users information and provides a quotation as componants are clicked. My componants' Listeners are in seperate inner classes and from these I want to add certain details to variables, it seems to compile and run but it doesn't seem to be changing the value of the variable when the componants are clicked, is there any reason why this happens, my code is below:
public class MyGUI extends JFrame{
        public MyGUI(){
          //GUI STUFF HERE
        double Price;
     private String total=calculate();
     public String calculate(){
          double aTotal=Price;
          return "$ " + aTotal;
     class MyListener implements ItemListener{
          public void itemStateChanged(ItemEvent evt){
               if(evt.getSource()==rad1) {
               Price=0.10;
               else if(evt.getSource()==rad2) {
               Price=0.12;
                    totalLab.setText(total);
}

shouldn't I also be able to access the outer classes methods? It doesn't seem to do this either.

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);
}

Why method local inner class can use final variable rather than....

Hi all
Just a quick question.
Why method-local inner class can access final variable defined in method only?
I know the reason why it can not access instance variable in method.
Just can not figure out why??
any reply would be appreciated.
Steven

Local classes can most definitely reference instance variables. The reason they cannot reference non final local variables is because the local class instance can remain in memory after the method returns. When the method returns the local variables go out of scope, so a copy of them is needed. If the variables weren't final then the copy of the variable in the method could change, while the copy in the local class didn't, so they'd be out of synch.

Hw To Make Inner Class Distinguish Func Parameter And Outer Class Var

i fail to make an inner class distinguish among function parameter and outer class variable.
consider the following code:
public class a {
     int var; // i want to access this one using inner class.
     public a(int var) {
          this.var = var;
          class b {
               public void fun() {
                    var = 100;
i get an error a.java:9: local variable var is accessed from within inner class; needs to be declared final.
when i change the code to this:
public class a {
     int var; // i want to access this one using inner class.
     public a() {
          class b {
               public void fun() {
                    var = 100;
it compiled no problem.it seems that inner class is accessing function parameter rather than outer class member.
is there any syntax i can use to make me access the outer class member variable whithout renaming or removing the function parameter?
thank you.

a.this.var = 100; //Use this in the inner class.Amazing syntax -:)

Inner class access to outer class variables

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