Prototype in Java

interface Prototype {   // 1. The clone()

Object clone();         //    contract

String getName();

}

interface Command {

void execute();

}                    

 

class PrototypesModule {       // 2. "registry" of prototypical objs

   private static Prototype[] prototypes = new Prototype[9];

   private static int         total      = 0;

   public static void addPrototype( Prototype obj ) {

      prototypes[total++] = obj;

   }

   public static Object findAndClone( String name ) {  // 4. The "virtual ctor"

      for (int i=0; i < total; i++)

         if (prototypes[i].getName().equals( name ))

            return prototypes[i].clone();

      System.out.println( name + " not found" );

      return null;

}  }

                                                  // 5. Sign-up for the clone()

class This implements Prototype, Command {        //    contract.  Each class 

   public Object clone()   { return new This(); } //    calls "new" on itself

   public String getName() { return "This"; }     //    FOR the client.

   public void   execute() { System.out.println( "This: execute" ); }

}

class That implements Prototype, Command {

   public Object clone()   { return new That(); }

   public String getName() { return "That"; }

   public void   execute() { System.out.println( "That: execute" ); }

}

class TheOther implements Prototype, Command {

   public Object clone()   { return new TheOther(); }

   public String getName() { return "TheOther"; }

   public void   execute() { System.out.println( "TheOther: execute" ); }

}

 

public class PrototypeDemo {

   public static void initializePrototypes() {    // 3. Populate the "registry"

      PrototypesModule.addPrototype( new This() );

      PrototypesModule.addPrototype( new That() );

      PrototypesModule.addPrototype( new TheOther() );

   }

   public static void main( String[] args ) {

      initializePrototypes();

      Object[] objects = new Object[9];

      int      total   = 0;

      for (int i=0; i < args.length; i++) {     // 6. Client does not use "new"

         objects[total] = PrototypesModule.findAndClone( args[i] );

         if (objects[total] != null) total++; }

      for (int i=0; i < total; i++) ((Command)objects[i]).execute();

}  }