Re: for :each style question

On 30/11/11 23:32, Roedy Green wrote:


If I needed it a lot...

import java.util.Arrays;
import java.util.List;

public class FirstLastLoop {
     interface FirstLastBlock<T> {
         void invoke(T t, boolean isFirst, boolean isLast);
     }

     static<T> void forEach(Iterable<? extends T> coll,
                             FirstLastBlock<? super T> block) {
         boolean isFirst = true;
         boolean lastHeld = false;
         T last = null;
         for (T t : coll) {
             if (lastHeld) {
                 block.invoke(last, isFirst, false);
                 isFirst = false;
             }

             last = t;
             lastHeld = true;
         }
         if (lastHeld)
             block.invoke(last, isFirst, true);
     }

     public static void main(String[] args) throws Exception {
         List<String> list = Arrays.asList(args);

         FirstLastBlock<String> block = new FirstLastBlock<String>() {
             public void invoke(String t, boolean isFirst, boolean isLast) {
                 if (isFirst)
                     System.out.print("The list: ");
                 else if (isLast)
                     System.out.print(" and ");
                 else
                     System.out.print(", ");
                 System.out.print(t);
                 if (isLast)
                     System.out.println('.');
             }
         };

         forEach(list, block);

         // Lambda version
         forEach(list, (t, isFirst, isLast) -> {
                 if (isFirst)
                     System.out.print("The list: ");
                 else if (isLast)
                     System.out.print(" and ");
                 else
                     System.out.print(", ");
                 System.out.print(t);
                 if (isLast)
                     System.out.println('.');
             });
     }
}

--
ss at comp dot lancs dot ac dot uk