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Chapter 6 - Objects and Classes (Part 4)
// Example 1
public class InnerInnerTest {
public static void main(String s[]) {
new Outer().new Inner().new
InnerInner().new InnerInnerInner().doSomething();
new Outer().new
InnerChild().doSomething();
new Outer2().new
Inner2().new InnerInner2().doSomething();
new InnerChild2().doSomething();
}
}
class Outer {
String name = "Vel";
class Inner {
String name =
"Sharmi";
class InnerInner {
class InnerInnerInner {
public void doSomething() {
// No problem in accessing without full qualification,
// inner-most class variable shadows the outer-most class variable
System.out.println(name); // Prints "Sharmi"
System.out.println(Outer.this.name); // Prints "Vel",
explicit reference to Outer
// error, variable is not
inherited from the outer class, it can be just accessible
//
System.out.println(this.name);
//
System.out.println(InnerInner.this.name);
//
System.out.println(InnerInnerInner.this.name);
// error, super cannot be used
to access outer class.
// super will always refer the
parent, in this case Object
//
System.out.println(super.name);
System.out.println(Inner.this.name); // Prints "Sharmi",
Inner has declared 'name'
}
}
}
}
/* This is an inner class extending an inner class in the
same scope */
class InnerChild extends Inner {
public void doSomething() {
// compiler error, explicit
qualifier needed
// 'name' is inherited from
Inner, Outer's 'name' is also in scope
// System.out.println(name);
System.out.println(Outer.this.name); // prints "Vel",
explicit reference to Outer
System.out.println(super.name); // prints "Sharmi", Inner
has declared 'name'
System.out.println(this.name); // prints "Sharmi", name
is inherited by InnerChild
}
}
}
class Outer2 {
static String name = "Vel";
static class Inner2 {
static String name =
"Sharmi";
class InnerInner2 {
public void doSomething() {
System.out.println(name); // prints "Sharmi", inner-most
hides outer-most
System.out.println(Outer2.name); // prints "Vel",
explicit reference to Outer2's static variable
//
System.out.println(this.name); // error, 'name' is not inherited
//
System.out.println(super.name); // error, super refers to Object
}
}
}
}
/* This is a stand-alone class
extending an inner class */
class InnerChild2 extends
Outer2.Inner2 {
public void doSomething() {
System.out.println(name); // prints "Sharmi", Inner2's
name is inherited
System.out.println(Outer2.name); // prints "Vel",
explicit reference to Outer2's static variable
System.out.println(super.name); // prints "Sharmi",
Inner2 has declared 'name'
System.out.println(this.name); // prints "Sharmi", name
is inherited by InnerChild2
}
}
// Example 2
public class InnerTest2 {
public static void main(String s[]) {
new OuterClass().doSomething(10, 20);
// This is legal
//
OuterClass.InnerClass ic = new OuterClass().new InnerClass();
//
ic.doSomething();
// Compiler error, local inner
classes cannot be accessed from outside
//
OuterClass.LocalInnerClass lic = new OuterClass().new
LocalInnerClass();
//
lic.doSomething();
new OuterClass().doAnonymous();
}
}
class OuterClass {
final int a = 100;
private String secret = "Nothing serious";
public void doSomething(int arg, final int fa) {
final int x = 100;
int y = 200;
System.out.println(this.getClass() + " - in
doSomething");
System.out.print("a = " + a + " secret = " +
secret + " arg = " + arg + " fa = " + fa);
System.out.println("
x = " + x + " y = " + y);
// Compiler error, forward
reference of local inner class
//
new LocalInnerClass().doSomething();
abstract class AncestorLocalInnerClass { } // inner class can be
abstract
final class LocalInnerClass extends AncestorLocalInnerClass { //
can be final
public void doSomething() {
System.out.println(this.getClass() + " - in
doSomething");
System.out.print("a = " + a );
System.out.print(" secret = " + secret);
//
System.out.print(" arg = " + arg); // Compiler error, accessing non-final argument
System.out.print(" fa = " + fa);
System.out.println(" x = " + x);
//
System.out.println(" y = " + y); // Compiler error,
accessing non-final variable
}
}
new InnerClass().doSomething(); // forward reference fine for
member inner class
new LocalInnerClass().doSomething();
}
abstract class AncestorInnerClass { }
interface InnerInterface { final int someConstant = 999;} //
inner interface
class InnerClass extends AncestorInnerClass implements
InnerInterface {
public void doSomething() {
System.out.println(this.getClass() +
" - in doSomething");
System.out.println("a = " +
a + " secret = " + secret + " someConstant = " +
someConstant);
}
}
public void doAnonymous() {
// Anonymous class implementing the inner interface
System.out.println((new InnerInterface() { }).someConstant);
// Anonymous class extending the inner class
( new InnerClass() {
public
void doSomething() {
secret = "secret is changed";
super.doSomething();
}
}
).doSomething();
}
}
|
Entity |
Declaration
Context |
Accessibility
Modifiers |
Outer
instance |
Direct
Access to enclosing context |
Defines
static or non-static members |
|
Package level class |
As package member |
Public or default |
No |
N/A |
Both static and non-static |
|
Top level nested class (static) |
As static class member |
All |
No |
Static members in enclosing context |
Both static and non-static |
|
Non static inner class |
As non-static class member |
All |
Yes |
All members in enclosing context |
Only non-static |
|
Local class (non-static) |
In block with non-static context |
None |
Yes |
All members in enclosing context + local final
variables |
Only non-static |
|
Local class (static) |
In block with static context |
None |
No |
Static members in enclosing context + local final
variables |
Only non-static |
|
Anonymous class (non-static) |
In block with non-static context |
None |
Yes |
All members in enclosing context + local final
variables |
Only non-static |
|
Anonymous class (static) |
In block with static context |
None |
No |
Static members in enclosing context + local final
variables |
Only non-static |
|
Package level interface |
As package member |
Public or default |
No |
N/A |
Static variables and non-static method prototypes |
|
Top level nested interface (static) |
As static class member |
All |
No |
Static members in enclosing context |
Static variables and non-static method prototypes |
Chapter 6 - Objects and Classes (Part 4)