Consider the code:

package net.rabbitware.core;

/**
 * Exception.
 *
 * @author alvin
 */
public class NewException extends Exception {
	private static final long serialVersionUID = 1L;

	/**
	 * Constructor.
	 *
	 * @param message
	 * the detail message
	 */
	public NewException(String message) {
		super(message);
	}

	/**
	 * Constructor.
	 *
	 * @param message
	 * the detail message
	 *
	 * @param cause
	 * the underlying cause of this exception
	 */
	public NewException(String message, Throwable cause) {
		super(message, cause);
	}
}


The two constructors give the "Utility class with visible constructor" warning.  It seems to only happen if you set a serialVersionUId.  I guess you can't get away with assuming any class which extends another class is not a utility class, but if a class extends a class which does not fit the criteria of a utility class, than AFAIK it's safe to assume the child class is also not a utility class.