MongoDB basicdbobject put method failure, reason of put Value failure and Solution

Basicdbobject cannot be put normally. Cause and solution of put Value failure

Basicdbobject OBJ=NewBasicdbobject ();

OBJ. Put (Key, value );

The error occurs because the key is unique.

If the key is the same, it overwrites the previous

For example:

OBJ. Put ("A", 1 );

OBJ. Put ("B", 2 );

OBJ. Put ("C", 3 );

OBJ. Put ("A", 5 );

After execution, only

OBJ. Put ("B", 2 );

OBJ. Put ("C", 3 );

OBJ. Put ("A", 5); // overwrite the previous obj. Put ("A", 1); because the keyword ""