A non-standard Javadoc inline tag was used, or was used in the wrong way. For example, @param should be used as a block tag to describe parameters, but cannot be used inline to link to parameters (prefer {@code paramName} for that).

/**
 * Doubles {@param n}.
 */
int twoTimes(int n) {
  return 2 * n;
}

/**
 * Doubles {@code n}.
 */
int twoTimes(int n) {
  return 2 * n;
}

If the @ symbol occurs inside a code excerpt, the fix is to escape the code excerpt using <pre>{@code ... }</pre>:

/**
 * Summary fragment.
 *
 * <pre>{@code
 * Your code here.
 * Can include <angle brackets>.
 * You can even include snippets that contain annotations, e.g.:
 * @Override public String toString() { ... }
 * }</pre>
 *
 * <p>Following paragraph.
 */

Suppression

Suppress by applying @SuppressWarnings("InvalidInlineTag") to the element being documented.