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+package design_patterns.observer_design_pattern;%0Aimport design_patterns.observer_design_pattern.Observer;%0A%0A/*%0A%09Interaface subject - to be implemented by all subjects%0A*/%0A%0Ainterface Subject%7B%0A%0A%09// register new observer%0A%09void register(Observer newob);%0A%0A%09// unregister existing observer%0A%09void unregister(Observer ob);%0A%0A%09// notify all observers of update%0A%09void updateAll();%0A%0A%0A%0A%7D

Add subject interface