How to I fix this error?

Exception in thread "main" java.lang.NumberFormatException: For input string: " "

at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)

at java.lang.Integer.parseInt(Integer.java:569)

at java.lang.Integer.parseInt(Integer.java:615)

at refrigerator.Refrigerator.main(Refrigerator.java:229)

/Users/home/Library/Caches/NetBeans/8.2/executor-snippets/run.xml:53: Java returned: 1

226 227 228 229 230 231 232 if(line.charAt(0)=='I') { } int item = Integer.parseInt(line.charAt(2)+""); int numRef = Integer.parseInt(line.charAt(4)+""); listRefs [numRef].insert_item(item); output = "Attempt to add "+item+" into refrigerator #"+numRef;