3.2 Java1492-plotting large quantities of data using java  (Page 19/27)

End of the PlotALot01 class

Listing 26 also signals the end of the overridden paint method, the end of the MyCanvas class, the end of the Page class, and the end of the PlotALot01 class. In short, Listing 26 signals the end of the class under discussion.

The class named PlotALot02

Much of the code in this class is very similar to the code in the class named PlotALot01 . Therefore, the discussion of this class will be much briefer than the earlier discussion of the class named PlotALot01 .

Designed for two-channel data

This class is an update to the class named PlotALot01 . This class is designed to plot large amounts of data for two channels on the same axes as shown in Figure 2 . One set of data is plotted using the color black. The other set of data is plotted using the color red.

As is the case for the class named PlotALot01 , this class provides a main method so that the class can be run as an application in self-test mode.

Three steps to use the class

As before, there are three steps involved in the use of this class for plotting data:

1. Instantiate a plotting object of type PlotALot02 .
2. Feed pairs of data values to the plotting object by calling the feedData method once for each pair of data values. The first value in the pair willbe plotted in black. The second value in the pair will be plotted in red.
3. Call the plotData method on the plotting object after all of the data has been fed to the object. This causes all of the data to be plotted. Italso causes the pages to be rearranged placing page 0 on the top of the stack.

A stack of page objects

The class produces a graphic output consisting of a stack of Page objects on the screen. Each Page object contains one or more horizontal axes on which the data is plotted as shown in Figure 2 . The two data sets are superimposed on the same axes with the data from one data set being plotted in black and the datafrom the other data set being plotted in red.

Testing with the main method

For test purposes, the main method instantiates a single plotting object and feeds two data sets to that plotting object. As before, the data that is fed tothe plotting object is white random noise. One of the data sets is the sequence of values obtained from a random number generator. The other data set is thesame as the first except that the sign of each data values is reversed.

Some data is not random

Also as before, and for the same reason, fifteen of the data values for eachdata set are not random. The non-random data values are the same as in the main method for the class named PlotALot01 . Figure 2 illustrates how these fifteen specific values are used to confirm the proper transition from the end of onetrace to the beginning of the next trace, and also to confirm the proper transition from the end of one page to the beginning of the next page.

The class named PlotALot02 and the main method

As before, I will discuss this class in fragments. A complete listing of the class is provided in Listing 36 near the end of the module. However, because much of the code in this class is very similar to code that I explained for theclass named PlotALot01 , this discussion of the code will be much briefer. I will highlight those aspects of this code that are different from the code in PlotALot01 .