Understanding Streams - Beginning Java - page 403

For example, you could write the following to output floating-point values:
double x = 27.5, y = 33.75;
String outString = String.format("x = %15.2f y = %14.3f", x, y);
outString contains the data formatted according to the first argument to the format() method. You
could pass outString to the print() method to output it to the command line:
System.out.print(outString);
You get the following output:
x = 27.50 y = 33.750
This is exactly the same output as you got earlier using the printf() method, but obviously outString
is available for use anywhere.
You can use a java.util.Formatter object directly to format data. You first create the Formatter ob-
ject like this:
StringBuffer buf = new StringBuffer();
java.util.Formatter formatter = new java.util.Formatter(buf);
The Formatter object generates the formatted string in the StringBuffer object buf — you could also
use a StringBuilder object for this purpose, of course. You now use the format() method for the format-
ter object to format your data into buf like this:
double x = 27.5, y = 33.75;
formatter.format("x = %15.2f y = %14.3f", x, y);
If you want to write the result to the command line, the following statement does it:
System.out.print(buf);
The result of executing this sequence of statements is exactly the same as from the previous fragment.
A Formatter object can format data and transfer it to destinations other than StringBuilder and
StringBuffer objects, but I defer discussion of this until I introduce file output in Chapter 10.
SUMMARY
In this chapter, I have introduced the facilities for inputting and outputting basic types of data to a stream.
You learned how to read data from the keyboard and how to format output to the command line. Of course,
you can apply these mechanisms to any character stream. You work with streams again when you learn
about reading and writing files.
EXERCISES
You can download the source code for the examples in the topic and the solutions to the following exer-
cises from www.wrox.com .
1. Use a StreamTokenizer object to parse a string entered from the keyboard containing a series of data
items separated by commas and output each of the items on a separate line.