How to quote "*/" in JavaDocs

Use HTML escaping.

So in your example:

/**
 * Returns true if the specified string contains "*/".
 */
public boolean containsSpecialSequence(String str)

/ escapes as a "/" character.

Javadoc should insert the escaped sequence unmolested into the HTML it generates, and that should render as "*/" in your browser.

If you want to be very careful, you could escape both characters: */ translates to */

Edit:

Follow up: It appears I can use / for the slash. The only downside is that this isn't all that readable when view the code directly.

So? The point isn't for your code to be readable, the point is for your code documentation to be readable. Most Javadoc comments embed complex HTML for explaination. Hell, C#'s equivalent offers a complete XML tag library. I've seen some pretty intricate structures in there, let me tell you.

Edit 2: If it bothers you too much, you might embed a non-javadoc inline comment that explains the encoding:

/**
 * Returns true if the specified string contains "*/".
 */
// returns true if the specified string contains "*/"
public boolean containsSpecialSequence(String str)

/**
 * Returns true if the specified string contains "*/".
 */

This is the ‘right’ solution, but for readability's sake I'd probably go for:

/**
 * Returns true if the string contains an asterisk followed by slash.
 */

Use the entity

*/ 

In your documentation it will show up as a "*/"

Another way I stumbled upon, just for completeness: add some HTML markup which doesn't alter the output between the * and /.

  /**
   * *<b/>/
   */

Compared to the HTML escape solution, this seems something of an ugly hack, but it also yields the right result in HTML output.

I would suggest you also add a line comment somewhere near saying something like

// */ is html for */