I think the core idea is for you to understand those data structures (from a language independent perspective), and then try and implement them using Java (since you already know the language). Get any good book on data structures and you should be able to take it from there.
If you just search for and use something you get online, you'll not be doing justice to your academics and that kinda makes the whole thing futile.
[NV added]
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With Java, Beans are used to represent data structures and can be read and written to databases using JDBC.
[Edit - Nish]
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@NV,
While that may be so, I believe the OP can write regular Java classes that represent data structures too, specially if the goal is to understand how these data structures work.
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