// Purpose. Inheritance run amok

public class DecoratorBefore {

static class A { public void doIt() { System.out.print( 'A' ); } }

static class AwithX extends A {
public void doIt() { super.doIt(); doX(); }
private void doX() { System.out.print( 'X' ); }
}

static class AwithY extends A {
public void doIt() { super.doIt(); doY(); }
public void doY() { System.out.print( 'Y' ); }
}

static class AwithZ extends A {
public void doIt() { super.doIt(); doZ(); }
public void doZ() { System.out.print( 'Z' ); }
}

static class AwithXY extends AwithX {
private AwithY obj = new AwithY();
public void doIt() {
super.doIt();
obj.doY();
} }

static class AwithXYZ extends AwithX {
private AwithY obj1 = new AwithY();
private AwithZ obj2 = new AwithZ();
public void doIt() {
super.doIt();
obj1.doY();
obj2.doZ();
} }

public static void main( String[] args ) {
A[] array = { new AwithX(), new AwithXY(), new AwithXYZ() };
for (int i=0; i < array.length; i++) {
array[i].doIt();
System.out.print( " " );
} } }

// AX AXY AXYZ



// Purpose. Decorator design pattern

public class DecoratorAfter {

interface I { void doIt(); }

static class A implements I { public void doIt() { System.out.print( 'A' ); } }

static abstract class D implements I {
private I core;
public D( I inner ) { core = inner; }
public void doIt() { core.doIt(); }
}

static class X extends D {
public X( I inner ) { super( inner ); }
public void doIt() {
super.doIt();
doX();
}
private void doX() { System.out.print( 'X' ); }
}

static class Y extends D {
public Y( I inner ) { super( inner ); }
public void doIt() {
super.doIt();
doY();
}
private void doY() { System.out.print( 'Y' ); }
}

static class Z extends D {
public Z( I inner ) { super( inner ); }
public void doIt() {
super.doIt();
doZ();
}
private void doZ() { System.out.print( 'Z' ); }
}

public static void main( String[] args ) {
I[] array = { new X( new A() ), new Y( new X( new A() ) ),
new Z( new Y( new X( new A() ) ) ) };
for (int i=0; i < array.length; i++) {
array[i].doIt();
System.out.print( " " );
} } }

// AX AXY AXYZ



// Purpose. Decorator design pattern

// 1. Create a "lowest common denominator" that makes classes interchangeable
// 2. Create a second level base class for optional functionality
// 3. "Core" class and "Decorator" class declare an "isa" relationship
// 4. Decorator class "hasa" instance of the "lowest common denominator"
// 5. Decorator class delegates to the "hasa" object
// 6. Create a Decorator derived class for each optional embellishment
// 7. Decorator derived classes delegate to base class AND add extra stuf
// 8. Client has the responsibility to compose desired configurations

interface Widget { void draw(); } // 1. "lowest common denominator"

class TextField implements Widget { // 3. "Core" class with "isa" rel
private int width, height;
public TextField( int w, int h ) {
width = w;
height = h;
}
public void draw() {
System.out.println( "TextField: " + width + ", " + height );
} }
// 2. Second level base class
abstract class Decorator implements Widget { // with "isa" relationship
private Widget wid; // 4. "hasa" relationship
public Decorator( Widget w ) { wid = w; }
public void draw() { wid.draw(); } // 5. Delegation
}

class BorderDecorator extends Decorator { // 6. Optional embellishment
public BorderDecorator( Widget w ) {
super( w );
}
public void draw() {
super.draw(); // 7. Delegate to base class
System.out.println( " BorderDecorator" ); // and add extra stuff
} }

class ScrollDecorator extends Decorator { // 6. Optional embellishment
public ScrollDecorator( Widget w ) {
super( w );
}
public void draw() {
super.draw(); // 7. Delegate to base class
System.out.println( " ScrollDecorator" ); // and add extra stuff
} }

public class DecoratorDemo {
public static void main( String[] args ) {
// 8. Client has the responsibility to compose desired configurations
Widget aWidget = new BorderDecorator(
new BorderDecorator(
new ScrollDecorator(
new TextField( 80, 24 ))));
aWidget.draw();
} }

// TextField: 80, 24
// ScrollDecorator
// BorderDecorator
// BorderDecorator



// Decorator - authenticate, input, encrypt, authenticate, decrypt, output

import java.io.*;

public class DecoratorStream {
static BufferedReader in = new BufferedReader( new InputStreamReader( System.in ) );

interface LCD {
void write( String[] s );
void read( String[] s );
}

static class Core implements LCD {
public void write( String[] s ) {
System.out.print( "INPUT: " );
try {
s[0] = in.readLine();
} catch (IOException ex) { ex.printStackTrace(); }
}
public void read( String[] s ) {
System.out.println( "Output: " + s[0] );
} }

static class Decorator implements LCD {
private LCD inner;
public Decorator( LCD i ) { inner = i; }
public void write( String[] s ) { inner.write( s ); }
public void read( String[] s ) { inner.read( s ); }
}

static class Authenticate extends Decorator {
public Authenticate( LCD inner ) { super( inner ); }
public void write( String[] s ) {
System.out.print( "PASSWORD: " );
try {
in.readLine();
} catch (IOException ex) { ex.printStackTrace(); }
super.write( s );
}
public void read( String[] s ) {
System.out.print( "PASSWORD: " );
try {
in.readLine();
} catch (IOException ex) { ex.printStackTrace(); }
super.read( s );
} }

static class Scramble extends Decorator {
public Scramble( LCD inner ) { super( inner ); }
public void write( String[] s ) {
super.write( s );
System.out.println( "encrypt:" );
StringBuffer sb = new StringBuffer( s[0] );
for (int i=0; i < sb.length(); i++)
sb.setCharAt( i, (char) (sb.charAt( i ) - 5) );
s[0] = sb.toString();
}
public void read( String[] s ) {
StringBuffer sb = new StringBuffer( s[0] );
for (int i=0; i < sb.length(); i++)
sb.setCharAt( i, (char) (sb.charAt( i ) + 5) );
s[0] = sb.toString();
System.out.println( "decrypt:" );
super.read( s );
} }

public static void main( String[] args ) {
LCD stream = new Authenticate( new Scramble( new Core() ) );
String[] str = { new String() };
stream.write( str );
System.out.println( "main: " + str[0] );
stream.read( str );
} }

// PASSWORD: secret
// INPUT: the quick brown fox
// encrypt:
// main: oc`lpd^f]mjriajs
// PASSWORD: secret
// decrypt:
// Output: the quick brown fox