Android How to Program, 3/e

J.10 Introduction to Files and Streams

Data stored in variables and arrays is temporary—it’s lost when a local variable goes out of scope or when the program terminates. For long-term retention of data, even after the programs that create the data terminate, computers use files. You use files every day for tasks such as writing a document or creating a spreadsheet. Data maintained in files is persistent data—it exists beyond the duration of program execution.

Files as Streams of Bytes

Java views each file as a sequential stream of bytes (Fig. J.10). Every operating system provides a mechanism to determine the end of a file, such as an end-of-file marker or a count of the total bytes in the file that’s recorded in a system-maintained administrative ...