1.1 --- a/task2/solution06/src/org/apidesign/apifest08/currency/Convertor.java Tue Oct 07 00:25:53 2008 +0200
1.2 +++ b/task2/solution06/src/org/apidesign/apifest08/currency/Convertor.java Tue Oct 07 00:46:19 2008 +0200
1.3 @@ -4,23 +4,44 @@
1.4
1.5 import java.math.BigDecimal;
1.6 import java.math.RoundingMode;
1.7 +import java.util.ArrayList;
1.8 import java.util.Currency;
1.9 +import java.util.List;
1.10
1.11 public final class Convertor {
1.12
1.13 - private final Currency first;
1.14 - private final Currency second;
1.15 - private final BigDecimal rateValue; // a rate between the first currency and the second currency
1.16 - public static final BigDecimal one = new BigDecimal(1);
1.17 + private List<ConvertorDelegate> convertorDelegates = new ArrayList<ConvertorDelegate>();
1.18
1.19 +
1.20 + /**
1.21 + * Create new instance of the converter for the given currencies and its rate.
1.22 + *
1.23 + * @param rateValue the rate between the first and the second currency
1.24 + * @param currencyFirst the first currency
1.25 + * @param currencySecond the second currency
1.26 + */
1.27 public Convertor(BigDecimal rateValue, Currency currencyFirst, Currency currencySecond) {
1.28 notNull(currencyFirst, "currencyFirst");
1.29 notNull(currencySecond, "currencySecond");
1.30 - notNull(rateValue, "rateValue");
1.31 + notNull(rateValue, "rateValue");
1.32 + convertorDelegates.add(new ConvertorDelegate(rateValue, currencyFirst, currencySecond));
1.33 + }
1.34 +
1.35 + /**
1.36 + * Create new instance of the convertor from the given convertors.
1.37 + * @param convertors the convertors
1.38 + */
1.39 + public Convertor(Convertor... convertors) {
1.40 + notNull(convertors, "convertors");
1.41 + if(convertors.length == 0) {
1.42 + throw new IllegalArgumentException("There must be at least one converter.");
1.43 + }
1.44
1.45 - this.rateValue = rateValue;
1.46 - this.first = currencyFirst;
1.47 - this.second = currencySecond;
1.48 + for(Convertor convertor: convertors) {
1.49 + if(convertor != null) {
1.50 + convertorDelegates.addAll(convertor.convertorDelegates);
1.51 + }
1.52 + }
1.53 }
1.54
1.55 /**
1.56 @@ -38,27 +59,66 @@
1.57 notNull(amount, "amount");
1.58 notNull(fromCurrency, "fromCurrency");
1.59 notNull(toCurrency, "toCurrency");
1.60 + ConvertorDelegate appropriateDelegate = null;
1.61
1.62 - if((fromCurrency != first && fromCurrency != second) || (toCurrency != first && toCurrency != second)) {
1.63 + //try find an appropriate delegate for conversion
1.64 + for(ConvertorDelegate delegate : convertorDelegates) {
1.65 + if(delegate.isConversionSupported(fromCurrency, toCurrency)) {
1.66 + appropriateDelegate = delegate;
1.67 + break;
1.68 + }
1.69 + }
1.70 +
1.71 + if(appropriateDelegate == null) {
1.72 throw new UnsupportedConversionException(fromCurrency, toCurrency);
1.73 - }
1.74 -
1.75 - BigDecimal rateValue = getRateValue(fromCurrency, toCurrency);
1.76 - BigDecimal result = rateValue.multiply(amount);
1.77 - return new Amount(result, toCurrency);
1.78 + }
1.79 +
1.80 + return appropriateDelegate.convert(amount, fromCurrency, toCurrency);
1.81 }
1.82
1.83 - private BigDecimal getRateValue(Currency fromCurrency, Currency toCurrency) {
1.84 + /**
1.85 + * Internal delegate implements a logic for conversion between two currencies
1.86 + * and vice versa.
1.87 + * @see #isConversionSupported(Currency, Currency)
1.88 + */
1.89 + private static class ConvertorDelegate {
1.90 + private final Currency first;
1.91 + private final Currency second;
1.92 + private final BigDecimal rateValue; // a rate between the first currency and the second currency
1.93 + public static final BigDecimal one = new BigDecimal(1);
1.94
1.95 - BigDecimal retVal;
1.96 -
1.97 - if(first == fromCurrency) {
1.98 - retVal = rateValue;
1.99 - } else {
1.100 - //reverse rate
1.101 - retVal = one.divide(rateValue, 10 ,RoundingMode.HALF_UP);
1.102 + private ConvertorDelegate(BigDecimal rateValue, Currency currencyFirst, Currency currencySecond) {
1.103 + this.rateValue = rateValue;
1.104 + this.first = currencyFirst;
1.105 + this.second = currencySecond;
1.106 }
1.107
1.108 - return retVal;
1.109 + private Amount convert(BigDecimal amount, Currency fromCurrency, Currency toCurrency) throws ConversionException {
1.110 + BigDecimal rateValue = getRateValue(fromCurrency, toCurrency);
1.111 + BigDecimal result = rateValue.multiply(amount);
1.112 + return new Amount(result, toCurrency);
1.113 + }
1.114 +
1.115 + private BigDecimal getRateValue(Currency fromCurrency, Currency toCurrency) {
1.116 +
1.117 + BigDecimal retVal;
1.118 +
1.119 + if(first == fromCurrency) {
1.120 + retVal = rateValue;
1.121 + } else {
1.122 + //reverse rate
1.123 + retVal = one.divide(rateValue, 10 ,RoundingMode.HALF_UP);
1.124 + }
1.125 +
1.126 + return retVal;
1.127 + }
1.128 +
1.129 + /**
1.130 + * @return <code>true</code> if the delegate is able to convert from the given currency
1.131 + * to the given currency and vice versa otherwise <code>false</code>.
1.132 + */
1.133 + private boolean isConversionSupported(Currency fromCurrency, Currency toCurrency) {
1.134 + return ((fromCurrency == first || fromCurrency == second) && (toCurrency == first || toCurrency == second));
1.135 + }
1.136 }
1.137 }
2.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
2.2 +++ b/task2/solution06/test/org/apidesign/apifest08/test/Task2Test.java Tue Oct 07 00:46:19 2008 +0200
2.3 @@ -0,0 +1,117 @@
2.4 +package org.apidesign.apifest08.test;
2.5 +
2.6 +import static org.apidesign.apifest08.test.Currencies.CZK;
2.7 +import static org.apidesign.apifest08.test.Currencies.USD;
2.8 +import static org.apidesign.apifest08.test.Currencies.SKK;
2.9 +
2.10 +import java.math.BigDecimal;
2.11 +
2.12 +import junit.framework.TestCase;
2.13 +import org.apidesign.apifest08.currency.Convertor;
2.14 +import org.apidesign.apifest08.test.Task1Test;
2.15 +
2.16 +/** There are many currencies around the world and many banks manipulate
2.17 + * with more than one or two at the same time. As banks are usually the
2.18 + * best paying clients, which is true even in case of your Convertor API,
2.19 + * it is reasonable to listen to their requests.
2.20 + * <p>
2.21 + * The quest for today is to enhance your existing convertor API to hold
2.22 + * information about many currencies and allow conversions between any of them.
2.23 + * Also, as conversion rates for diferent currencies usually arise from various
2.24 + * bank departments, there is another important need. There is a need to
2.25 + * compose two convertors into one by merging all the information about
2.26 + * currencies they know about.
2.27 + */
2.28 +public class Task2Test extends TestCase {
2.29 + public Task2Test(String testName) {
2.30 + super(testName);
2.31 + }
2.32 +
2.33 + @Override
2.34 + protected void setUp() throws Exception {
2.35 + }
2.36 +
2.37 + @Override
2.38 + protected void tearDown() throws Exception {
2.39 + }
2.40 +
2.41 + // As in Task1Test, keep in mind, that there are three parts
2.42 + // of the whole system:
2.43 + // 1. there is someone who knows the current exchange rate
2.44 + // 2. there is someone who wants to do the conversion
2.45 + // 3. there is the API between 1. and 2. which allows them to communicate
2.46 + //
2.47 + // Please backward compatibly enhance your existing API to support following
2.48 + // usecases:
2.49 + //
2.50 +
2.51 + /** Create convertor that understands two currencies, CZK and
2.52 + * SKK. Make 100 SKK == 75 CZK. This is method for the group of users that
2.53 + * knows the exchange rate, and needs to use the API to create objects
2.54 + * with the exchange rate. Anyone shall be ready to call this method without
2.55 + * any other method being called previously. The API itself shall know
2.56 + * nothing about any rates, before this method is called.
2.57 + */
2.58 + public static Convertor createTripleConvertor() {
2.59 + // Rates: 1USD = 15CZK
2.60 + // Rates: 1USD = 20SKK
2.61 + // Rates: 75CZK = 100SKK
2.62 + Convertor usdCzk = new Convertor(new BigDecimal(15), USD, CZK);
2.63 + Convertor usdSkk = new Convertor(new BigDecimal(20), USD, SKK);
2.64 + Convertor skkCzk = new Convertor(new BigDecimal("0.75"), SKK, CZK);
2.65 + return new Convertor(new Convertor[]{usdCzk, usdSkk, skkCzk});
2.66 + }
2.67 +
2.68 + /** Define convertor that understands three currencies. Use it.
2.69 + */
2.70 + public void testConvertorForUSDandCZKandSKK() throws Exception {
2.71 + Convertor c = createTripleConvertor();
2.72 +
2.73 + // convert $5 to CZK using c:
2.74 + assertEquals("Result is 75 CZK", 75 ,c.convert(new BigDecimal(5), USD, CZK).getValue().intValue());
2.75 +
2.76 + // convert $5 to SKK using c:
2.77 + assertEquals("Result is 100 SKK", 100, c.convert(new BigDecimal(5), USD, SKK).getValue().intValue());
2.78 +
2.79 + // convert 200SKK to CZK using c:
2.80 + assertEquals("Result is 150 CZK", 150, c.convert(new BigDecimal(200), SKK, CZK).getValue().intValue());
2.81 +
2.82 + // convert 200SKK to USK using c:
2.83 + assertEquals("Result is 10 USD", 10, c.convert(new BigDecimal(200), SKK, USD).getValue().intValue());
2.84 + }
2.85 +
2.86 + /** Merge all currency rates of convertor 1 with convertor 2.
2.87 + * Implement this using your API, preferably this method just delegates
2.88 + * into some API method which does the actual work, without requiring
2.89 + * API clients to code anything complex.
2.90 + */
2.91 + public static Convertor merge(Convertor one, Convertor two) {
2.92 + return new Convertor(new Convertor[]{one, two});
2.93 + }
2.94 +
2.95 + /** Join the convertors from previous task, Task1Test and show that it
2.96 + * can be used to do reasonable conversions.
2.97 + */
2.98 + public void testConvertorComposition() throws Exception {
2.99 + Convertor c = merge(
2.100 + Task1Test.createCZKtoUSD(),
2.101 + Task1Test.createSKKtoCZK()
2.102 + );
2.103 +
2.104 + // convert $5 to CZK using c:
2.105 + assertEquals("Result is 85 CZK", 85, c.convert(new BigDecimal(5), USD, CZK).getValue().intValue());
2.106 +
2.107 + // convert $8 to CZK using c:
2.108 + assertEquals("Result is 136 CZK", 136, c.convert(new BigDecimal(8), USD, CZK).getValue().intValue());
2.109 +
2.110 + // convert 1003CZK to USD using c:
2.111 + assertEquals("Result is 59 USD", 59, c.convert(new BigDecimal(1003), CZK, USD).getValue().intValue());
2.112 +
2.113 + // convert 16CZK using c:
2.114 + assertEquals("Result is 20 SKK", 20, c.convert(new BigDecimal(16), CZK, SKK).getValue().intValue());
2.115 +
2.116 + // convert 500SKK to CZK using c:
2.117 + assertEquals("Result is 400 CZK", 400, c.convert(new BigDecimal(500), SKK, CZK).getValue().intValue());
2.118 +
2.119 + }
2.120 +}