Problem
Imagine that your application is meant to process an XML file. It is given a tag and needs to find a "special tag" that this tag might be nested in. This problem has several solutions. I tackled a similar problem some time ago and I will present you with some of the solutions that I considered.
While loop
private SpecialTag findSpecialTag()
{
Tag parent = this.getParentTag();
while (parent != null && !(parent instanceof SpecialTag))
{
parent = parent.getParentTag();
}
return (SpecialTag) parent;
}
Do-while loop
private SpecialTag findSpecialTag()
{
Tag parent = this;
do
{
parent = parent.getParentTag();
}
while (parent != null && !(parent instanceof SpecialTag));
return (SpecialTag) parent;
}
Recursion
private SpecialTag findSpecialTag()
{
return findSpecialTag(this.getParentTag());
}
private SpecialTag findSpecialTag(Tag tag)
{
if (tag == null || tag instanceof SpecialTag)
{
return (SpecialTag) tag;
}
else
{
return findSpecialTag(tag.getParentTag());
}
}
Solution
In my personal opinion, I find the while loop cleanest and simplest to understand. Do-while loop gets a bit messy with the condition at the end and recursion is probably the worst. I find recursion a bit hard to follow. It can also introduce an extra method just for its own sake (as in this example).
I do not have a strong opinion on this topic. If you like to program recursions, while loops, do-while loops, or for loops, it's fine by me. I certainly will not change your code, but if you ask me to write some code, it'd most likely be a while (or for) loop.
I use while and for loops interchangeably. The previous example with while loop would look like this with for loop:
private SpecialTag findSpecialTag()
{
Tag p = this.getParentTag();
for(; p != null && !(p instanceof SpecialTag); p = p.getParentTag());
return (SpecialTag) parent;
}
What is your preference?
