Many applets accessing a writing servlet ...

Question

i have a game - applet which includs a highscore. to save the scores permanently theres also a servlet for accessing the server resources. so if theres a new highscore reached the applet sends it to ther servlet, which writes the score in a txt-file on the server.
but im smelling problems if several applets are running at the same time:
for each applet instance a unique servlet connection is created for highscore entry. so only crap would happen if one connection writes to the file, another one reads at the same time and so on.
how can i safely synchronize the data ?
btw: for this project i have no access to a database (which would make many problems obsolete ...)

Answer 1

thought about something similar but theres the question about how to realize the lock. if servlet instance A gets an update an writes to the file, a variable gets locked ( perhaps over a static variable ? is every servlet instance accessing the same static var like in "normal" applications ?). then servlet B posts the new score in a query (then static, too). hmmm, now which one writes the query ? perhaps the servlet which just wrote and then tests if there are more to write ? it shouldnt happen, that different servlet feel responsible for writing the query ...