I'm not a java developer, naturally I work with C# but i know storing passwords in plain text is not a safe way to store them.
As far as I know; you can decompile java, in which case you will be able to read the passwords without a problem. If you are running an open source project with source code in a repository somewhere; storing this password in plain text is going to be a much bigger problem than storing it in the database.
Personally I feel like any password should be encrypted using a strong up-to-date algorithm which you do not create yourself but use a trusted and reliable library to do this for you.
Just general looking around it appears that using char is far better than using a string because strings are immutable.
As a reference I have come across an article which explains some best
practises for storing passwords:
char vs string storing passwords:
I have no personal experience in Java development as mentioned; but i'd be very concerned seeing passwords stored in plain text.