Java™ How to Program, Seventh Edition

14.1. Introduction

Storage of data in variables and arrays is temporary—the data is lost when a local variable goes out of scope or when the program terminates. Computers use files for long-term retention of large amounts of data, even after the programs that created the data terminate. You use files every day for tasks such as writing an essay or creating a spreadsheet. We refer to data maintained in files as persistent data because it exists beyond the duration of program execution. Computers store files on secondary storage devices such as hard disks, optical disks and magnetic tapes. In this chapter, we explain how Java programs create, update and process files.

File processing is one of the most important capabilities a language must have ...