Java Reference
In-Depth Information
Let's add an instance variable to the outer class and access that instance variable inside the inner class. To keep
the example simple, you have added a new
getValue()
method to the
Inner
class in order to access the
Outer
class's
instance variable called
dummy
. The modified code is as follows:
public class Outer {
int dummy = 101;
public class Inner {
public int getValue() {
// Access Outer's class dummy field
int x = dummy + 200;
return x;
}
}
}
The decompiled code for
Outer.class
and
Outer$Inner.class
files are as follows:
// Decompiled code from Outer.class file
public class Outer {
int dummy = 0;
public Outer() {
dummy = 101;
}
}
// The decompiled code from Outer$Inner.class file
public class Outer$Inner {
final Outer this$0;
public Outer$Inner(Outer outer) {
this$0 = outer;
super();
}
public int getValue() {
int x = this$0.dummy + 200;
return x;
}
}
Note the use of
this$0.dummy
to access the instance variable of the
Outer
class inside the
getValue()
method
of the
Inner
class. The
dummy
instance variable in the
Outer
class has a package-level access. Since an inner class is
always the part of the same package as its enclosing class, this method of referring to the instance variable of the
Outer
class from outside works fine. However, if the instance variable
dummy
is declared
private
, the
Outer$Inner
class code
cannot refer to it directly as it did in the previous example. The compiler uses a different way to access the
private
instance variable of the outer class from an inner class. The following is the modified code and the corresponding
decompiled code for the
Outer
and
Inner
classes:
// Modified Outer class code with dummy as private instance variable
public class Outer {
private int dummy = 101; // Declare dummy as private
