CollectionClassifier.java

// Broken! - What does this program print?
package org.effectivejava.examples.chapter07.item41;

import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class CollectionClassifier {
	public static String classify(Set<?> s) {
		return "Set";
	}

	public static String classify(List<?> lst) {
		return "List";
	}

	public static String classify(Collection<?> c) {
		return "Unknown Collection";
	}

	public static void main(String[] args) {
		Collection<?>[] collections = { new HashSet<String>(),
				new ArrayList<BigInteger>(),
				new HashMap<String, String>().values() };

		for (Collection<?> c : collections)
			System.out.println(classify(c));
	}
}