Updated some aspects, merged changes from Ottavio.

Author: atsticks

src/main/java/org/javamoney/moneta/ExchangeRateBuilder.java

@@ -5,6 +5,7 @@
 import javax.money.convert.ConversionContext;
 import javax.money.convert.ExchangeRate;
 import javax.money.convert.RateType;
+
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
@@ -173,4 +174,16 @@ public ExchangeRateBuilder setRate(ExchangeRate rate){
         this.term = rate.getCurrency();
         return this;
     }
+
+	@Override
+	public String toString() {
+		StringBuilder sb = new StringBuilder();
+		sb.append("org.javamoney.moneta.ExchangeRateBuilder: ");
+		sb.append("[conversionContext").append(conversionContext).append(',');
+		sb.append("base").append(base).append(',');
+		sb.append("term").append(term).append(',');
+		sb.append("factor").append(factor).append(',');
+		sb.append("rateChain").append(rateChain).append(']');
+		return sb.toString();
+	}
 }

src/main/java/org/javamoney/moneta/ExchangeRateType.java

@@ -0,0 +1,69 @@
+package org.javamoney.moneta;
+
+import javax.money.convert.ExchangeRateProviderSupplier;
+
+import org.javamoney.moneta.convert.internal.ECBCurrentRateProvider;
+import org.javamoney.moneta.convert.internal.ECBHistoric90RateProvider;
+import org.javamoney.moneta.convert.internal.ECBHistoricRateProvider;
+import org.javamoney.moneta.convert.internal.IMFRateProvider;
+import org.javamoney.moneta.convert.internal.IdentityRateProvider;
+
+/**
+ * <p>
+ * This enum contains all implementation of moneta. Using this enum will easier
+ * to choose an available implementation.
+ * </p>
+ * <code>ExchangeRateProvider provider = MonetaryConversions.getExchangeRateProvider(ExchangeRateType.ECB);<code>
+ * 
+ * @author otaviojava
+ */
+public enum ExchangeRateType implements ExchangeRateProviderSupplier {
+	/**
+	 * Exchange rate to the European Central Bank. Uses the
+	 * {@link ECBCurrentRateProvider} implementation.
+	 */
+	ECB("ECB", "Exchange rate to the European Central Bank."),
+	/**
+	 * Exchange rate to the International Monetary Fond. Uses the
+	 * {@link IMFRateProvider} implementation.
+	 */
+	IMF("IMF", "Exchange rate to the International Monetary Fond."),
+	/**
+	 * Exchange rate to European Central Bank (last 90 days). Uses the
+	 * {@link ECBHistoric90RateProvider} implementation.
+	 */
+	ECB_HIST90("ECB-HIST90",
+			"Exchange rate to European Central Bank (last 90 days)."),
+	/**
+	 * Uses the {@link ECBHistoricRateProvider} implementation.
+	 */
+	ECB_HIST(
+			"ECB-HIST",
+			"Exchange rate to the European Central Bank that loads all data up to 1999 into its historic data cache."),
+	/**
+	 * Uses the {@link IdentityRateProvider} implementation.
+	 */
+	IDENTITY(
+			"IDENT",
+			"Exchange rate rate with factor one for identical base/term currencies");
+
+	private String type;
+
+	private String description;
+
+	ExchangeRateType(String type, String description) {
+		this.type = type;
+		this.description = description;
+	}
+
+	@Override
+	public String get() {
+		return type;
+	}
+
+	@Override
+	public String getDescription() {
+		return description;
+	}
+
+}

src/main/java/org/javamoney/moneta/convert/internal/DefaultMonetaryConversionsSingletonSpi.java

@@ -15,18 +15,24 @@
  */
 package org.javamoney.moneta.convert.internal;
 
-import org.javamoney.moneta.spi.CompoundRateProvider;
-import org.javamoney.moneta.spi.MonetaryConfig;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 
 import javax.money.MonetaryException;
 import javax.money.convert.ConversionQuery;
 import javax.money.convert.ExchangeRateProvider;
 import javax.money.spi.Bootstrap;
 import javax.money.spi.MonetaryConversionsSingletonSpi;
-import java.util.*;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.logging.Level;
-import java.util.logging.Logger;
+
+import org.javamoney.moneta.spi.CompoundRateProvider;
+import org.javamoney.moneta.spi.MonetaryConfig;
 
 /**
  * This is the default implementation of the {@link javax.money.spi.MonetaryConversionsSingletonSpi} interface, backing