File input$/$output $($I$/$O$)$ operations are essential for reading from and writing to external files in Java applications. Explore the intricacies of file I$/$O in Java, including the various classes and methods available in the java.io package. How do file streams facilitate reading and writing data to files, and what are the potential challenges and best practices associated with file handling? Additionally, how can Java's exception handling mechanisms be utilized to manage errors and exceptions that may occur during file I$/$O operations? Lastly, discuss the implications of using file I$/$O for data persistence and sharing across different Java applications or platforms.