/*
 * File:  DataList.java
 *
 * A class with an instance variable that is an ArrayList 
 */

import java.util.ArrayList;

/**
 * Computes the average, maximum, and standard deviation of any 
 * number of scores
 */
public class DataList 
{
   // instance var
   private ArrayList<Integer> scores ;          // list of scores
     
   /**
    * Creates an empty data set
    */
   public DataList()
   {
       scores = new ArrayList<Integer>() ;
   }
   
   /**
    * Adds a score to the DataSet
    * @param next the score to be added
    */
   public void addScore(int next)
   {
       scores.add(next) ;       // calls add method of ArrayList class
   }
   
   /**
    * Returns a string containing all the scores in the DataSet
    * @return all the scores
    */
   public String toString()
   {
       String scoreString = "" ;        // create empty string

       // for each score in the set
       for (int i = 0 ; i < scores.size() ; i ++)
       {
           int current = scores.get(i) ;        // get next score
           scoreString += current + "  " ;      // concatenate to string
       }
       return scoreString ;
   }
   
   /**
    * Returns the average of the scores in the DataSet
    * @return the average score
    */
   public double getAverage()
   {
       int sum = 0 ;
       for (int i = 0 ; i < scores.size() ; i ++)
       {
           int current = scores.get(i) ;
           sum = sum  + current ;
       }
       return (double)sum / scores.size() ;
   }
   
   /**
    * Returns the largest score in the DataSet
    * @return the largest score
    */
   public int getMaximum()
   {
       int max = scores.get(0) ;            // assume first score is largest
       
       // check all other scores
       for (int i = 1 ; i < scores.size() ; i ++)
       {
           int nextScore = scores.get(i) ;  // get next score
           if (nextScore > max)             // if greater than current max...
           {
               max = nextScore ;            // ...save as new max
           }
       }
       return max ;
   }
   
   /**
    * Computes and returns the population standard deviation
    * @return the population standard deviation
    */
   public double getStanDev()
   {
       // 1. get the average of all the scores
       double average = this.getAverage() ;
       
       // 2. compute the sum of the squares of the differences between
       //    each score and the average
       
       double sumOfSquares = 0.0 ;
       
       // for each score on list
       for (int i = 0 ; i < scores.size() ; i ++)
       {
           int current = scores.get(i) ;        // gets next score
           double diff = current - average ;    // difference from average
           sumOfSquares += Math.pow(diff,2) ;   // add square of difference
       }                                        // to accumulator

       // 3. divide by number of scores
       double variance = sumOfSquares / scores.size() ;

       // 4. standard deviation is square root of the variance
       return Math.sqrt(variance) ;
   }

   public boolean isEmpty()
   {
        return scores.size() == 0 ;
   }
}