SourceMaking

interface Strategy { public void solve(); }          // 1. Define the interface

                                                     //    of the algorithm

abstract class TemplateMethod1 implements Strategy { // 2. Bury implementation

   public void solve() {                             // 3. Template Method 

      start();

      while (nextTry() && ! isSolution())

         ;

      stop();

   }

   protected abstract void    start();

   protected abstract boolean nextTry();

   protected abstract boolean isSolution();

   protected abstract void    stop();

}

 

class Impl1 extends TemplateMethod1 {

   private int state = 1;

   protected void    start()   { System.out.print( "start  " ); }

   protected void    stop()    { System.out.println( "stop" ); }

   protected boolean nextTry() {

      System.out.print( "nextTry-" + state++ + "  " );

      return true; }

   protected boolean isSolution() {

      System.out.print( "isSolution-" + (state == 3) + "  " );

      return (state == 3);

}  }

 

abstract class TemplateMethod2 implements Strategy { // 2. Bury implementation

   public void solve() {                             // 3. Template Method

      while (true) {

         preProcess();

         if (search()) break;

         postProcess();

   }  }

   protected abstract void    preProcess();

   protected abstract boolean search();

   protected abstract void    postProcess();

}

 

class Impl2 extends TemplateMethod2 {

   private int state = 1;

   protected void    preProcess()  { System.out.print( "preProcess  " ); }

   protected void    postProcess() { System.out.print( "postProcess  " ); }

   protected boolean search() {

      System.out.print( "search-" + state++ + "  " );

      return state == 3 ? true : false;

}  }

 

public class StrategyDemo {    // 4. Clients couple strictly to the interface

   public static void clientCode( Strategy strat ) { strat.solve(); }

   public static void main( String[] args ) {

      Strategy[] algorithms = { new Impl1(), new Impl2() };

      for (int i=0; i < algorithms.length; i++)

         clientCode( algorithms[i] );

}  }