DesignPattern,Design Pattern,DesignPatterns,Design Patterns,Design Patterns Java,DesignPatternsJava,J2EE,Java,Java Design Patterns,JavaDesignPatterns,Software Design Patterns,SoftwareDesignPatterns,enterprisearchitecture,Java Programming Language,Java Web Development,Software Development,J2EE patterns,Observer pattern,Observerpattern,ObserverDesignPattern,Observer design pattern,observer design pattern in java,observer pattern in java