Constructor that takes a password, salt, iteration count for generating PBEKey of fixed-key-size PBE ciphers. An empty char[] is used if null is specified for password.

Note: the password and salt are cloned before they are stored in the new PBEKeySpec object.

Parameters:

password     the password.

salt     the salt.

iterationCount     the iteration count.

Exceptions:

NullPointerException if salt is null.

IllegalArgumentException if salt is empty, i.e. 0-length, or iterationCount is not positive.

`password`		the password.
`salt`		the salt.
`iterationCount`		the iteration count.

`NullPointerException`		if `salt` is null.
`IllegalArgumentException`		if `salt` is empty, i.e. 0-length, or `iterationCount` is not positive.