Hibernate-将hql查询映射到HashMap <String, String>

Question

I've already looked at the post here:

With Hibernate, how can I query a table and return a hashmap with key value pair id>name?

And that has a beautiful answer, but what if I want the key of my HashMap to be a String with spaces? Or other characters for that matter?

Answer 1

This will work fine...think about how a HashMap works...it's backed by a hash table. If you have some String , we'll call it key , then by the Java specification the hashCode() method of any object has to be deterministic, ie return the same hash code value when called on an object for the life of the instance of the JVM it's running in.

Spaces will not affect the hash code of a String object. Adding spaces to a string will make it a different String and therefore result in a different hash code. See for yourself:

public static void main(String[] args) {
    Map<String, String> someMap = new HashMap<String, String>();

    someMap.put("some random key", "value");

    System.out.println(someMap.get("some random key"));
    System.out.println(" some random key ".hashCode()); // prints 1846300114
    System.out.println("some random key".hashCode()); // prints -2030143442

}