10.11

Consider the partially completed Coin class below. A Coin has a year it made mintYear, a value at the time it was made faceValue and the country of origin.

public class Coin{ private int mintYear; //year coin was made private double faceValue; //value of coin at time it was made private String country; //origin country public Coin(int year, double value, String ctry){ mintYear = year; faceValue = value; country = ctry; } //other constructors and methods not shown public int getYear(){ return mintYear; } }

The CoinCollection class has an ArrayList of Coins. The constructor of the CoinCollection class takes arrays for the years, values and countries. These arrays are parallel arrays. Thus if I have three coins: A US quarter from 1900, a US dime from 1910 and a US nickel from 1920, the arrays would contain: Years = { 1900, 1910, 1920} Values = { 0.25, 0.10, 0.05} Countries = { "US", "US", "US"} The partially completed CoinCollection class is below.

public class CoinCollection{ private ArrayList coins; //collection of coins //precondition: parallel arrays of all the same length //write the constructor of CoinCollection for part A public CoinCollection(int[] years, double[] values, String[] countries){ //to be completed in part A } //there may be other constructors and methods not shown }

Part A Write the CoinCollection constructor. The USCoinCollection class extends the CoinCollection class. A partially completed CoinCollection and USCoinCollection classes are below:

import java.util.ArrayList; public class CoinCollection{ private ArrayList coins; //collection of coins //precondition: parallel arrays of all the same length //write the constructor of CoinCollection for part A public CoinCollection(int[] years, double[] values, String[] countries) { } //there may be other constructors methods not shown } public class USCoinCollection extends CoinCollection { //precondition: parallel arrays of all the same length //write the constructor of CoinCollection for part A public USCoinCollection() { super(years, values, countries); } //there may be other constructors methods not shown }

Part B A rare coin in one that was minted prior to a certain year. A rare coin collection will have all coins minted prior to a certain year. The isRare() method takes a year parameter and determines if a coin collection is rare. Below is the method header for the isRare() method:

public boolean isRare(int year) { } Given a CoinCollection myCoins with the following coins: 1930 Mexico 1.00, 1925 US 0.25, 1925 Britain 0.05 Given a USCoinCollection usCoins with the following coins: 1925 US 0.25, 1920 US 0.50, 1908 US 1.00

myCoins.isRare(1930) would return false usCoins.isRare(1930) would return true

Identify which class(es) the isRare() method belongs in and write out the method below.

Rubric:

Part A

• Instantiation of the Coin ArrayList
• Loop set up correctly (initialization, termination, counter, no bounds error)
• Add to the ArrayList correctly
• Constructing new Coin object
• Correct parameters in Coin object

Part B

• Correct placement of method in CoinCollection class (point not awarded if in the USCoinCollection or both classes)
• Looping through the Coin ArrayList with no bounds error
• Correct comparison of coin to the rareYear
• Returning true if and only if all coins have a mint year before the rareYear parameter
• Returning false if one or more of the coin years is not less than the rareYear parameter