Job Ready Java

Lesson 24Using Simple File Input and Output

Up to this point, we have been dealing with data as variables (primitives and objects) in memory and occasionally reading values from the console (and then promptly storing these values in a variable). This has worked well, but all of our data disappears when the program completes. To write truly useful programs, we must be able to store data when program execution ends and read that data the next time we run our programs.

In this lesson, we will begin to explore data persistence and ways that we can translate data from variables (in memory) to files (on disk) for long-term storage and then reverse the process when we need to access the data later. We will concentrate on storing data in flat text files for now, but the principles of this lesson continue to be relevant when we start storing data in relational databases.

We will also take a look at one way we can do simple file input and output. For now, however, we'll cover the basics—just enough to get data into and out of files.

LEARNING OBJECTIVES

By the end of this lesson, you will be able to:

• Describe options for data storage
• Describe how related data is represented in object-oriented languages
• Define marshaling and unmarshaling
• Explain the characteristics of a file format
• Create a plan to write data to and read data from a file
• Write to a file using PrintWriter
• Use Scanner to read from a file

DATA STORAGE AND REPRESENTATION

We have two options available to us for data ...