import java.util.*;

class LoopDemo {
    
    static double sum_v1( List<Double> data ) {
        if (data.isEmpty()) {
            return 0.0;
        }
        else {
            return data.get(0) + sum_v1(data.subList(1,data.size()));
        }
    }   

    
    
    static double sum_v2( List<Double> data ) {
        double sumSoFar = 0.0;
        while (!data.isEmpty()) {
            sumSoFar = sumSoFar + data.get(0);
            data = data.subList(1,data.size());
        }
        return sumSoFar;
    }
    
    static double min_v2( List<Double> data ) {
        double minSoFar = data.get(0);
        while (!data.isEmpty()) {
            minSoFar = Math.min( minSoFar, data.get(0) );
            data = data.subList(1,data.size());
            }
        return minSoFar;
        }

    /* Return a new list, like `data` but with all elements reversed. 
     */
    List<Double> reverse_v2( List<Double> data ) {
        List<Double> reversalSoFar = new ArrayList<Double>();
        while (!data.isEmpty()) {
            reversalSoFar.add(0, data.get(0));
            data = data.subList(1,data.size());
        }
        return reversalSoFar;
    }

   
        
        
        
    
    static List<Double> numsDown( int n ) {
      if (n==0) {
        return new ArrayList<Double>();
        }
      else {
        /* return numsDown(n-1).add(0, (double)n);*/
        List<Double> restNumsDown = numsDown(n-1);
        restNumsDown.add(0, (double)n);
        // `add` is a void method, so I can't combine with the preceding or following line.
        return restNumsDown;
        }
      }


    public static void main( String[] args ) {
      System.out.println( "Expect: 0.  Got: " + sum_v1( new ArrayList<Double>() ));
      System.out.println( "Expect: 12.  Got: "
                          + sum_v1(Arrays.asList( 5.0, 2.0, 4.0, 1.0 )) );
      System.out.println( "Expect: 0.  Got: " + sum_v2( new ArrayList<Double>() ));
      System.out.println( "Expect: 12.  Got: "
                          + sum_v2(Arrays.asList( 5.0, 2.0, 4.0, 1.0 )) );
    }

      
      
}


/*
 ; To sort in Java:
   class Asteroid implements Comparable {
       double x,y;
       
       int compareTo( /* Asteroid this, */ /* Asteroid that ) {
           return (this.sz - that.sz);
       }
    }
       */