Question

I tested with java.util.IdentityHashMap, See

public class IdentityHashMapTest{
    public static void main(String args[]) {
        Map<String, String> m = new IdentityHashMap<String, String>();
        m.put("John", "Doe");
        m.put("John", "Paul");
        System.out.println(m.size());
    }
}

According to Java API said,

This class implements the Map interface with a hash table, using reference-equality in place of object-equality when comparing keys (and values)

The result may be 2. But actual is 1. Is IdentityHashMap class wrong?

Answer 1

Change it to

       m.put("John", "Doe");
       m.put(new String("John"), "Paul");

and it will have two entries. String literals are pooled, so "John" == "John".