Why is char[] preferred over String for passwords?

Question

In Swing, the password field has a getPassword() (returns char[]) method instead of the usual getText() (returns String)

Answer 1

Some people believe that you have to overwrite the memory used to store the password once you no longer need it. This reduces the time window an attacker has to read the password from your system and completely ignores the fact that the attacker already needs enough access to hijack the JVM memory to do this. An attacker with that much access can catch your key events making this completely useless (AFAIK, so please correct me if I am wrong).

Update

Thanks to the comments I have to update my answer. Apparently there are two cases where this can add a (very) minor security improvement as it reduces the time a password could land on the hard drive. Still I think it's overkill for most use cases.

• Your target system may be badly configured or you have to assume it is and you have to be paranoid about core dumps (can be valid if the systems are not managed by an administrator).
• Your software has to be overly paranoid to prevent data leaks with the attacker gaining access to the hardware - using things like TrueCrypt (discontinued), VeraCrypt, or CipherShed.

If possible, disabling core dumps and the swap file would take care of both problems. However, they would require administrator rights and may reduce functionality (less memory to use) and pulling RAM from a running system would still be a valid concern.