Merge pull request #27 from sgrimm-sg/exchange

Fix DefaultExchangeRate's equals and hashCode methods

Author: Otávio Santana

src/main/java/org/javamoney/moneta/convert/DefaultExchangeRate.java

@@ -16,6 +16,7 @@
 package org.javamoney.moneta.convert;
 
 import java.io.Serializable;
+import java.math.BigDecimal;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
@@ -251,7 +252,24 @@ public String toString() {
      */
     @Override
     public int hashCode() {
-        return Objects.hash(base, conversionContext, factor, term, chain);
+        // Numerically equal factors should produce the same hash code, so hash a normalized
+        // version of the factor rather than the NumberValue object.
+        BigDecimal normalizedFactor = factor.numberValue(BigDecimal.class).stripTrailingZeros();
+
+        // The exchange rate chain includes a reference to "this" if the caller doesn't explicitly
+        // set a chain in the builder, so we can't naively hash the chain or we'll get infinite
+        // recursion.
+        int chainHash = 0;
+        for (ExchangeRate chainedRate : chain) {
+            if (chainedRate == this) {
+                // Use a constant to represent the presence of this object in the chain.
+                chainHash = Objects.hash(chainHash, "this");
+            } else {
+                chainHash = Objects.hash(chainHash, chainedRate);
+            }
+        }
+
+        return Objects.hash(base, conversionContext, normalizedFactor, term, chainHash);
     }
 
     /*
@@ -268,7 +286,8 @@ public boolean equals(Object obj) {
             DefaultExchangeRate other = (DefaultExchangeRate) obj;
             return Objects.equals(base, other.base) &&
                     Objects.equals(conversionContext, other.conversionContext) &&
-                    Objects.equals(factor, other.factor) && Objects.equals(term, other.term);
+                    factor.compareTo(other.factor) == 0 &&
+                    Objects.equals(term, other.term);
         }
         return false;
     }

src/test/java/org/javamoney/moneta/function/ExchangeRateSimpleTest.java

@@ -26,13 +26,16 @@
 import org.javamoney.moneta.spi.DefaultNumberValue;
 import org.testng.annotations.Test;
 
+import java.math.BigDecimal;
+
 public class ExchangeRateSimpleTest {
     private static final CurrencyUnit EUR = Monetary.getCurrency("EUR");
     private static final CurrencyUnit GBP = Monetary.getCurrency("GBP");
 
     @Test
     public void equalsTest() {
         DefaultNumberValue factor = new DefaultNumberValue(1.1);
+        DefaultNumberValue bigDecimalFactor = new DefaultNumberValue(new BigDecimal("1.1"));
 
         ExchangeRate rate1 = new ExchangeRateBuilder("myprovider", RateType.ANY)
                 .setBase(EUR)
@@ -46,6 +49,15 @@ public void equalsTest() {
                 .setFactor(factor)
                 .build();
 
-        assertEquals(rate1, rate2);
+        ExchangeRate rate3 = new ExchangeRateBuilder("myprovider", RateType.ANY)
+                .setBase(EUR)
+                .setTerm(GBP)
+                .setFactor(bigDecimalFactor)
+                .build();
+
+        assertEquals(rate1, rate2, "Rates with same factor");
+        assertEquals(rate1, rate3, "Rates with numerically equal factor");
+        assertEquals(rate1.hashCode(), rate2.hashCode(), "Hashes with same factor");
+        assertEquals(rate1.hashCode(), rate3.hashCode(), "Hashes with numerically equal factor");
     }
 }