Is there a way to return an immutable hashtable??????

[Vinney Shanmugam]

Is there a way to return a non-mutable hashtable. Below is my code and i have got a comment as to return an non-mutable hashtable. I dont have much idea on this. Please help me find this. Are there any classes avilable to acheive this???

>>>>>>>>>>>>>>>>
private Hashtable list_users;

public Hashtable getUsers() {
//TODO
// Is it prudent to return an object of type Hashtable. This makes the contents of the hashtable vulnerable ???
// It is better to return a non-mutable hashtable
return list_users;
}
>>>>>>>>>>>>>>>>

[Campbell Ritchie]

Don't know. It is worthwhile going through the Java Tutorials for collections, and also the Map interface. There are some methods in Collections which return a read-only Collection, which can only me altered by its "home" class and not by the recipient. There might be away to do that with Maps; I don't know.
Alternatively, create a wrapper class which implements Map, and throw an Exception (UnsupportedOperationException) if anybody uses the put remove clear, etc methods.

Actually, I think this question is too difficult for beginners: moving it.

[Jelle Klap]

Well, java.util.Hashtable implements the java.util.Map interface, so you can use the java.utilCollections#unmodifiableMap to return an immutable view of a Hashtable.
You should be aware that any attempts to structurally modify the Hashtable via the reference returned by the unmodifiableMap() method will cause an UnsupportedOperationException.

[Vinney Shanmugam]

thanks for your replies....

yeah, i googled and found some useful information....

we can use Collections.unmodifiablemap() method which will return a map which can't be tampered with.
Still if there are any valuable inputs please give them.....

[Campbell Ritchie]

vinod shan wrote:thanks for your replies....