How to resolve java.lang.NumberFormatException: For input string: "N/A"?

How to resolve java.lang.NumberFormatException: For input string: "N/A"?

In my debugging I am getting the exception like this:
java.lang.NumberFormatException: For input string: "N/A"
at java.lang.NumberFormatException.forInputString(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at java.lang.Integer.valueOf(Unknown Source)
at java.util.TreeMap.compare(Unknown Source)
at java.util.TreeMap.put(Unknown Source)
at java.util.TreeSet.add(Unknown Source)`
How to resolve the error?