Could Not parse java.lang.NumberFormat Exception

Question

try{    
    if (flag_conv == false)
    {
      if ((Integer.parseInt(et1.getText().toString()))<=55)
      {
       final AlertDialog alertDialog = new AlertDialog.Builder(this).create();
       alertDialog.setTitle("Reset...");
       alertDialog.setMessage("WB should be grater than 55");

       alertDialog.setButton2("OK", new DialogInterface.OnClickListener() {
          public void onClick(DialogInterface dialog, int which) 
          {
                // here you can add functions
                dialog.dismiss();
          }});
       alertDialog.setIcon(R.drawable.icon);
       alertDialog.show();
       tv1.setText("WB");
       et1.setText("");
       wbflg = true;
       wbval = 0;
       return;          
     }
     else
     {                     
      wbval = Integer.parseInt(et1.getText().toString());
     }
   }
 catch(NumberFormatException nfe)
{System.out.println("Could not parse " + nfe);}

And i got the following Exception

07-31 14:48:45.409: INFO/System.out(431): Could not parse java.lang.NumberFormatException: unable to parse '' as integer
07-31 14:48:50.569: INFO/System.out(431): Could not parse java.lang.NumberFormatException: unable to parse '' as integer
07-31 14:48:54.599: INFO/System.out(431): Could not parse java.lang.NumberFormatException: unable to parse '' as integer
07-31 14:48:54.829: INFO/System.out(431): Could not parse java.lang.NumberFormatException: unable to parse '' as integer
07-31 14:48:54.958: INFO/System.out(431): Could not parse java.lang.NumberFormatException: unable to parse '' as integer
07-31 14:48:55.108: INFO/System.out(431): Could not parse java.lang.NumberFormatException: unable to parse '' as integer
07-31 14:48:55.259: INFO/System.out(431): Could not parse java.lang.NumberFormatException: unable to parse '' as integer
07-31 14:48:55.409: DEBUG/dalvikvm(118): GREF has increased to 201
07-31 14:48:55.429: INFO/System.out(431): Could not parse java.lang.NumberFormatException: unable to parse '' as integer
07-31 14:52:43.798: DEBUG/SntpClient(58): request time failed: java.net.SocketException: Address family not supported by protocol

Answer 1

On Integer.parseInt

The exception message seems to be the following:

07-31 14:48:45.409: INFO/System.out(431): Could not parse
   java.lang.NumberFormatException: unable to parse '' as integer

Indeed, an empty string can not be parsed by Integer.parseInt(String). Thus:

int num = Integer.parseInt("");
// throws java.lang.NumberFormatException: For input string: ""

If you have an arbitrary String s which can be isEmpty() or even null, then you must have special code to handle it, because Integer.parseInt(s) will always throw an exception in those cases.

Of course Integer.parseInt(s) can throw NumberFormatException when s is e.g. "xyz", so you may want to put the statement inside a try-catch block.

So you can write something like this:

String s = ...;
if (s == null || s.isEmpty()) {
   complaintAboutNotGettingAnything();
} else {
   try {
     int num = Integer.parseInt(s);
     doSomethingWith(num);
   catch (NumberFormatException e) {
     complaintAboutGettingSomethingYouDontWant();
   }
}

---

On writing code that is easy to debug

In this particular snippet, it looks like parseInt is invoked as follows:

if ((Integer.parseInt(et1.getText().toString()))<=55) ...

A lot of things can go wrong in this one expression. I suggest refactoring that breaks this apart into logical observable steps as follows:

String et1text = et1.getText().toString();
// maybe check if it's empty/null if necessary
// maybe log/inspect what the value of et1text is for debugging

try {
   int et1val = Integer.parseInt(et1text);
   if (et1val <= THRESHOLD) {
      // ...
   }
} catch (NumberFormatException e) {
   moreComplaining();
}

Answer 2

I am not sure about Java but if you have strings which might not be valid ints you may have a function like in C# of:

bool res = Int.TryParse(s,ref int);