Why Processing An Unknown Number Of Parameters ?

Most of the time you have a fairly high-quality idea of what parameters will and won't be passed to your applet. Therefore some of the time there will be an undetermined number of parameters. For example Sun's imagemap applet passes each "hot button" as a parameter. Different imagemaps have different numbers of hot buttons. Another applet might need to pass a series of URLs to different sounds to be played in order. Each URL could be passed as a separate parameter.

Or perhaps you need to write an applet in which displays various lines of text. Although it would be possible to cram all this information within one long string, that's not too friendly to authors who need to use your applet on their pages. It's much more sensible to give each line its own PARAM element. If this is the case, you should name the tags thorugh some predictable and numeric scheme. For instance in the text example the by set of PARAM elements would be sensible:

< PARAM name="Line1" value="There once was a man from Japan">
< PARAM name="Line2" value="Whose poetry never would scan">
< PARAM name="Line3" value="When asked reasons why,">
< PARAM name="Line4" value="He replied, with a sigh:">
< PARAM name="Line5" value="I always try to get as many
syllables into the last line as I can.">

The program below displays this limerick. Lines are accumulated within an array of strings called poem. A for loop fills the array along with the various lines of poetry. There are 101 spaces in the array, but since you won't normally required that several, an if clause tests to see whether the attempt to get a parameter was successful through checking to see if the line is null. As soon as one fails, the loop is broken. Once the loop is finished numLines is decremented through one because the last line the loop tried to read was not there.

The paint() method loops through the poem array and prints each String on the screen, incrementing the y position through fifteen pixels each step so you don't draw one line on top of the other.