Tree Structure Implementation in Java.

Question

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How should i implement a "Tree Structure" in Java Based application.?How would i map the entries to the database table?how many tables will i require for this implementation.?
List records<String> = new ArrayList<String>();
records.add("null");
records.add("Product");
records.add("Category");
records.add("P1");
records.add("P2");
records.add("P3");
records.add("C1");
records.add("C2");
records.add("C3");
so how should i implement a Tree Structure for the above record set.
//P1,P2,P3 belong to Parent {Product}
//C1,C2,C3 belong to Parent {Category}
Sample code provided will be helpful

Answer 1

How should i implement a "Tree Structure" in Java Based application.?The quotes suggest you don't know what a tree structure is, regardless of the development language. Fix that first (your understanding of what a tree structure is). [url http://en.wikipedia.org/wiki/Tree_structure]Here is probably a good start.
How would i map the entries to the database table?how many tables will i require for this implementation.?It depends on what your tree structure represents, in particular it depends on whether the leaves and intermediate nodes of the trees have are homogeneous (e.g. have a common interface). There is no general rule.
I suggest you start by looking in the Java API at all the classes whose names start with 'Tree' (TreeSet and TreeMap are probably the best ones to start with) and read the documentation carefully. Then try to write some code that uses one and come back if/when you have any problems.(sorry Winston) I think this is a very bad advice.
These classes are particular implementations, respectively of a set (in the mathematical sense) and of a map (associative table), which happen to use a "tree structure" for their internal business. Their API doesn't help building a custom "tree structure" (they may be used that way, but it's certainly not the easiest nor even a particular handy way to build tree structures).
Maybe their implementation may be a good example of how to build a Tree structure, but they use a particular type of tree (+red-black tree), not a general one. This may or may not be the OP's case, I wouldn't bet on it.
OP you're welcome to come back with more specific questions and details. Good luck with Java.
Edited by: jduprez on Oct 16, 2010 2:45 PM
Edited by: jduprez on Oct 16, 2010 2:49 PM
After checking the Javadoc: indeed TreeSet only uses a TreeMap for its implementation, so the only one out of the two which does directly uses a tree structure in its implementation is TreeMap.
Edited by: jduprez on Oct 16, 2010 2:51 PM
And, to reiterate, I stand by my claim that TreeMap is not a good example of a general Tree structure: in particular it uses a tree to map keys to values, its main business is the "mapping" part, not the tree as a storage medium. Neither the keys nor the values know anything about their "children".