Try to use another constructor:
public FileOutputStream (File file, boolean append)
Constructs a new FileOutputStream that writes to file. If append is true and the file already exists, it will be appended to; otherwise it will be truncated. The file will be created if it does not exist.
But I think that the default constructor is already overwriting the existing file
public FileOutputStream (String path)
Constructs a new FileOutputStream that writes to path. The file will be truncated if it exists, and created if it doesn't exist.