The document discusses several design patterns including strategy, template method, factory method, command, state, null object, and dependency injection. It provides examples of how each pattern can be implemented in code by defining interfaces and classes that implement the pattern. The examples demonstrate how different design patterns address common programming problems by organizing code in a reusable and flexible manner.

2.  M


3. public class Shape{
protected int h,w;
public void setWidth(int w){
this.w = w;
}
public void setHeight(int h){
this.h = h; →
}
}
public class Rectangele extends Shape{
}
public class Square extends Rectangle{
protected int h,w;
public void setWidth(int w){
this.w = w; →
this.h = h;
}
public void setHeight(int h){
this.w = w;
this.h = h;
}
}

4. LSP
public class Shape{
protected int h,w;
ArrayList<Rectangele> list
public void setWidth(int w){ = new ArrayList<Rectangele>();
this.w = w;
}
public void setHeight(int h){ for(Rectangler r : list){
}
this.h = h; r.setWidth(20);
} r.setHeight(10);
}
public class Rectangele extends Shape{
}
public class Square extends Rectangle{
protected int h,w;
public void setWidth(int w){
this.w = w;
this.h = h;
} List Square
public void setHeight(int h){
this.w = w;
this.h = h;
}
}

5. public class User{
public void dosth(Shape s){ public Interface Shape{
s.dosth(); public void dosth();
} }
}
public class Rectangle implements Shape{ public class Square implements Shape{
public void dosth(){ public void dosth(){
System.out.println(“do something”); System.out.println(“do something”);
} }
} }
Light Weight
POJP Plain Old Java Object

6. 
 Gof
 23 new
 →

7.  Temprate Method
 Strategy
 Factory Method
 Command
 State
 Null Object

8. Template Method
public abstract class DBInterface{ public class OracleInterface extends DBInterface{
public Date getData(){ protected void init(){
init(); //
Data data = getData();
exit();
return data; }
} protected Data getData(){
protected abstract void init(); //
protected abstract Data getData(); }
protected abstract void exit(); protected void exit(){
} //
}
extends }ublic class FireBirdInterface extends DBInterface{
p
////
}
 Data

 DBInterface
=
=public

9. Strategy
public Interface DBInterface{ public class OracleInterface implements DBInterface{
public void init(); public void init(){
public Data getData(); //
public void exit(); }
} public Data getData(){
//
}
implements public void exit(){
//
}
}
public class FireBirdInterface implements DBInterface{
////
}
 Template

 DBInterface

10. Template Method Strategy
public class TemlePrinter { Template Method
main(){
DBInterface di = new OracleInterface();
print(di.getData()); uses
} getData()
}
public class StratPrinter {
main(){ Strategy
DBInterface di = new OracleInterface();
di.init()
print(di.getData()); uses init() getData()
di.exit();
} exit()
}
 Template Method Strategy
 = Template Method
Strategy
Strategy init
DB Template Method

11. Factory Method
public Interface Bond{
public Interface BondFactory{ creates public int getMaturity();
public Bond getBondInstance();
public BigDecimal getFairValue();
}
}
implements implements
public class TreasuryFactory implements BondFactory{ public class Treasury implements Bond{
public Bond getBondInstance(){ ////
return new Treasury(); }
}
}
public class ConvertibleFactory implements BondFactory{ public class Convertible implements Bond{
public Bond getBondInstance(){ ////
return new Convertible();
}
}
}


 Bond Strategy Template
Factory Factory

12. Command
public class User{
public void dosth(Tranzaction t,String id){
t.do(id); public Interface Tranzaction{
} public void do(String id);
} }
public class addCommand implements Tranzaction{
public void do(String id){
//
}
}
public class removeCommand implements Tranzaction{
public void do(String id){
//
}
}

13. State
public class User{
State s = n;
public void dosth(){ public Interface State{
s.do(); public int do();
} }
}
public class GoodState implements State{
public void do(){
System.ouit.println(“Good State”);
}
}
public class BadState implements State{
public void do(){
System.ouit.println(“Good State”);
}
}

14. Null Object
Null
public class User{
public void dosth(Tranzaction t,String id){ public Interface Tranzaction{
t.do(id); public void do(String id);
} }
}
public class NullCommand implements Tranzaction{
public void do(String id){
//
}
}

15. DI Dipendency Injection
public class User{
public void dosth(Tranzaction t,String id){
t.do(id); public Interface Tranzaction{
} public void do(String id);
} }
DI
Tranzaction
public class removeCommand implements Tranzaction{
public void do(String id){
//
}
}

16. DI
 new
–
–
 DI
– Spring
– Seaser2
– EJB 3.0

17. Strategy/Temprate Method
DI