Android™ How to Program, Second Edition

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.