File Handling

Abstract

With all our programs so far, there has been a very fundamental limitation: all data accepted is held only for as long as the program remains active. As soon as the program finishes execution, any data that has been entered and the results of processing such data are thrown away. Of course, for very many real-life applications (banking, stock control, financial accounting, etc.), this limitation is simply not realistic. These applications demand persistent data storage. That is to say, data must be maintained in a permanent state, such that it is available for subsequent further processing. The most common way of providing such persistent storage is to use disc files. Java provides such a facility, with the access to such files being either serial or random. The following sections explain the use of these two file access methods, firstly for non-GUI applications and later for GUI applications. In addition, the important and often neglected topic of serialisation is covered.