public class Lab6 {

  // an interface for entities which have a value
  public static interface Valuable {
    public int getValue();
  }
  
  // a simple class which implements the Valuable interface.
  // its value is the value of the number.
  public static class ValNum implements Valuable {
    private int value;
    public ValNum(int value) { this.value = value; }
    public int getValue() { return value }
    public void setValue(int value) { this.value = value; }
  }

  // another class with a value: this contains an array, and its
  // value is the sum of its positive elements (negative ones are ignored)
  public static class TotalArray implements Valuable {
    private int[] arr;
    public TotalArray(int[] arr) { this.arr = arr; }
    
    public int getValue() {
      // this will sum up every positive number in arr,
      // and return the total sum
      int sum = 0;
      int i = 0;
      while (arr[i] > 0 && i < arr.length) {
        sum += arr[i];
        i++;
      }
    }
  }

  public static void main(String[] args) {
    
    // declare three variables: a value-number and two value-arrays 
    ValNum num = new ValNum(5);
    TotalArray tarr1 = new TotalArray( new int[]{1, 2, 3} );
    TotalArray tarr2 = new TotalArray( new int[]{1, 2, -3, 2, 1} );
    
    // a list of valuables containing the number and both arrays from above
    Valuable[] valuables = { num, tarr1, tarr2 };
    
    // print what's inside of each
    for (Valuable v : valuables) System.out.println( v.getValue() );
  }
}