— Scott McNealy, Sun Microsystems Chairman, President and ceo

private int x;

 MyInner inner = new MyInner();
public void doStuff() {
inner.go();
}

class MyInner {
void go() {
x = 42;
}
} 
// close inner class
} 
// close outer class
The outer class has a private 
instance variable ‘x’
Make an instance of the 
inner class
The method in the inner class uses the 
outer class instance variable ‘x’, as if ‘x’ 
belonged to the inner class.
If you instantiate an inner class from code within an outer class, the instance 
of the outer class is the one that the inner object will ‘bond’ with. For 
example, if code within a method instantiates the inner class, the inner 
object will bond to the instance whose method is running.
Code in an outer class can instantiate one of its own inner classes, in exactly 
the same way it instantiates any other class... 
new MyInner()
How to make an instance of an inner class
MyOuter
outer
MyInner
inner
int
x
MyOuter
outer
int
x
special 
bond
You can instantiate an inner instance from code running outside the outer class, but you 
have to use a special syntax. Chances are you’ll go through your entire Java life and never 
need to make an inner class from outside, but just in case you’re interested..
.

 class Foo {
public static void main (String[] args) {
MyOuter outerObj = new MyOuter();
MyOuter.MyInner innerObj = outerObj.new MyInner();
}
}
inner class 
instances
Side bar
call a method on the 
inner class

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