Quickly...valid variable names

[Matt Kidd]

Working through the deitel book and I'm back in chapter 2 reviewing the questions. With regards to variable names I said all these were valid
_under_bar_, m928134, t5, j7, her_sales$, his_$account_total, a, b$, c, z, z2, h22

I said all these were invalid 3g, 87, 67h2, h22, 2h.

Am I correct?

[nupur dhawan]

You are correct, except for one thing....h22 is a valid variable .
In your answer it seems to appear as both valid and invalid, which i'm sure is just a mistake and wanted to point it out to you .

[Matt Kidd]

yes...typo on my part. Meant to put h22 up with the valid ones. Okay back to the book.

[Dirk Schreckmann]

While you're reading that book, I recommend that you frequently take a look at The Java Language Specification. Section 3.8 on identifiers answers your question.
Another strategy to answer such questions, that I strongly recommend, is that you don't fully believe what the book or anybody here says, and you write a quick test program to answer the question(s).
Good Luck.