public class Ex7 {
private int fld;
private void meth(int val) {
fld = val;
System.out.println(" meth() -> fld = " + fld);
}
public class Ex7Inner1 {
void operateOnFld() {
fld = 12;
}
void operateOnMeth() {
meth(10);
}
public void bar() {
System.out.println(" bar() ");
}
}
class Ex7Inner2 {
Ex7Inner1 i1 = new Ex7Inner1();
// how to call i1.bar() ??
i1.bar();
}
}
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Have you tried this? What happened? I haven't tried it, but I have my doubts that your inner public class is actually going to be public, but it should work.James Black– James Black2009-09-10 17:10:44 +00:00Commented Sep 10, 2009 at 17:10
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the answer doesn't actually have anything to do with inner classes, its a basic syntax error.skaffman– skaffman2009-09-10 17:11:41 +00:00Commented Sep 10, 2009 at 17:11
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I missed the problem with Ex7Inner2. I am waiting for Eclipse to start up.James Black– James Black2009-09-10 17:19:03 +00:00Commented Sep 10, 2009 at 17:19
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4 Answers
Your problem is that you need to call i1.bar() inside a function. For example
class Ex7Inner2 {
Ex7Inner1 i1 = new Ex7Inner1(); // this is now a field of the Ex7Inner2 class
public void callBar() {
i1.bar(); // this will work
}
}
In the future, you may find that people are able to be more helpful if you include the error you get in your question, which I'll do now. When you try to compile the code your way, you get an error that looks like
Ex7.java:26: <identifier> expected
i1.bar();
^
1 error
This is because the only thing you can do outside of a method (like you originally had it) is declare variables. So it was expecting an "identifier" by which it meant "the name of the variable you are declaring". So if you had said
String s;
then s would have been the identifier.
2 Comments
Flueras Bogdan
now i feel that this was a dumb question.. how could i have wrote such code?
Eli Courtwright
Haha, I often find myself asking the same question about my own code. Don't let it get you down - you're not alone!
A few things wrong here;
- your inner2 needs to be calling the i1 inside of a function
- since you didn't declare inner1 static it needs an instance of the enclosing Ex7 to exist.
So you can do something like this:
public class Ex7 {
private Ex7Inner1 i1;
public class Ex7Inner1 {
public void bar() {
System.out.println( " bar() " );
}
}
class Ex7Inner2 {
// how to call i1.bar() ??
public Ex7Inner2() {
Ex7.this.i1.bar();
}
}
}
To access the Ex7's i1.
Where your Ex7 instance contains an inner1 and an inner2 and your reference from within inner2 is inner2-->parentEx7 -->child inner1.
If you make the inner class static you can do away with the Ex7 reference, as you're defining that the inner class doesn't need an instance of the outer class to exist.
Comments
Ex7Inner1 needs a reference to Ex7 in order to instantiate. From Ex7Inner2 that reference is Ex7.this.
Thus say
Ex7Inner1 i1 = Ex7.this.new Ex7Inner1()
See the Java Tutorial from more information.
