Hello!

I need a answer quick
How can I check if a key is already taken in a hashtable ?
I wanted to loop in all object in the hastable but I can not see how to loop because in hashtable we do not have any index...Any one can help me ?

This is an example of what I want to do:
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I have added 3 elements in my hastable:

myHashTable.put ("101", Object1);
myHashTable.put ("1241", Object2;
myHashTable.put ("19, Object3;

Now i need a piece of code to loop in the hashtable to be able to check the key of each...how can i do that ???