Does StringBuilder.toString retain the built string?

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http://stackoverflow.com – I'm creating a StringBuilder to collect strings that I periodically flush to a server. If the flush fails, I want to keep the strings to try again next time, although in the mean time I might get additional strings to send which must be added to the StringBuilder. What I want to know is what the most efficient way to do this would be, as this is being done in an Android app where battery usage and thus CPU usage is a big concern. Does calling StringBuilder's toString() function store the resulting string it returns internally so that a subsequent call doesn't have to do the work of copying (HowTos)