TypeSafeMap.java

package uk.co.optimisticpanda.test;

import java.util.HashMap;
import java.util.Map;

/**
 * Supporting subset of map operations based on the key containing type information.
 */
public class TypeSafeMapTest {

	public static class Key<T> {

		private final String key;

		public Key(String key) {
			this.key = key;
		}

		@SuppressWarnings("unchecked")
		public T get(Map<?, ?> map) {
			return (T) map.get(key);
		}

		@SuppressWarnings("unchecked")
		public T put(Map<? super Object, ? super Object> map, T value) {
			return (T) map.put(key, value);
		}
		
		@SuppressWarnings("unchecked")
		public T remove(Map<? super Object, ? super Object> map) {
			return (T) map.remove(key);
		}
	}

	public static class TypeSafeMap {

		private final Map<Object, Object> map = new HashMap<Object, Object>();

		public <T, A extends Key<T>> T get(A key) {
			return key.get(map);
		}

		public <T, A extends Key<T>> T put(A key, T value) {
			return key.put(map, value);
		}
		
		public <T, A extends Key<T>> T remove(A key) {
			return key.remove(map);
		}  
	}

	public static void main(String[] args) {
		Key<String> NAME = new Key<>("name");
		Key<Long> AGE = new Key<>("age");

		TypeSafeMap safeMap = new TypeSafeMap();
		safeMap.put(NAME, "Andrew");
		safeMap.put(AGE, 234L);
		
		String name = safeMap.get(NAME);
		Long age = safeMap.get(AGE);
		
		System.out.println(name + ", " + age);
	}
}