在不覆盖Java的情况下写入文本文件

I am trying to write a method that makes a "log.txt file" if one does not already exist and then writes to the file. The problem that I am encountering is every time I call the method, it overwrites the existing log. How do I change the method so that instead of overwriting the data it just updates the file?I am trying to write a method that makes a "log