Alternate Suggestion

Example.java

import java.util.Set;

public class Example {

	public static void main(final String[] args) {
		
		final ParamMap<Param.ICE> map = (ParamMap<ICE>) new DummyParamMap();
		
		final Price VWAP = map.get(ICE.SESSION_VWAP);
		
		final Size size = map.get(ICE.TEST_SIZE);
		
		System.out.println(VWAP);
		System.out.println(size);
		
	}
	
	public static class DummyParamMap implements ParamMap<ICE> {

		final Price vwap = Price.ONE;
		final Size size = Size.ONE;
		
		@SuppressWarnings("unchecked")
		@Override
		public <V> V get(ICE param) {
			
			switch((Param.ICE)param) {
				default:
					throw new IllegalArgumentException();
				case SESSION_VWAP:
					return (V) ((Param.ICE) param).type().cast(vwap);
				case TEST_SIZE:
					return (V) ((Param.ICE) param).type().cast(size);
			}
		}

		@Override
		public boolean has(ICE param) {
			return false;
		}

		@Override
		public Set<ICE> keySet() {
			return null;
		}
		
	}
	
}

Explanation.txt

This might be useful a useful alternative? It avoids ambivalent enum pileup inside of Param that are "cross-exchange" (containing Param keys associated with more than one Exchange in the same Param enum). Compiles and works...

Param.java

import com.barchart.util.value.api.Price;
import com.barchart.util.value.api.Size;

public class Param<K extends Enum<K>> {
	private K type;
	
	public Param(K type) {
		this.type = type;
	}
	
	
	public K type() { return type; }
	
	
	
	public enum CME {
		
		SESSION_CME(Price.class),
		
		TEST_SIZE(Size.class)
		
		;
		
		private final Class<?> clazz;
		
		private CME(final Class<?> clazz) {
			this.clazz = clazz;
		}
		
		@SuppressWarnings("unchecked")
		public <V> Class<V> type() {
			return (Class<V>) clazz;
		}
		
	}
	
	public enum ICE {
			
		SESSION_VWAP(Price.class),
		
		TEST_SIZE(Size.class)
		
		;
		
		private final Class<?> clazz;
		
		private ICE(final Class<?> clazz) {
			this.clazz = clazz;
		}
		
		@SuppressWarnings("unchecked")
		public <V> Class<V> type() {
			return (Class<V>) clazz;
		}
		
	}
	
}

ParamMap.java

import java.util.Set;

public interface ParamMap<K extends Enum<K>> {

	<V> V get(K param);
	
	boolean has(K param);
	
	Set<K> keySet();
}