Generating numerical test data is easy with Java. It boils down to using a java.util.Random object to generate random numbers.
Listing 2-13 Generating random numeric data
This program generates the following CSV file of eight rows and five columns of random decimal values.
Figure 2-9 Test data file
Metadata is data about data. For example, the preceding generated file could be described as eight lines of comma-separated decimal numbers, five per line. That's metadata. It's the kind of information you would need, for example, to write a program to read that file.
That example is quite simple: the data is unstructured and the values are all the same type. Metadata about structured data must also describe that structure.
The metadata of a dataset may be included in the same file as the data itself. The preceding example could be modified with a header line like this:
Figure 2-10 Test data file fragment with metadata in header