Looking for a way to handle java.lang.NumberFormatException: empty String

Question

I'm new to programming and I'm learning on the go.

I've got my app to do everything i need it to but when my text fields are empty and the calculate button is hit the app shuts down and i get java.lang.NumberFormatException: empty String. At this point i can't figure out how to avoid this.

/** Pull data from edittext **/
double ang = Double.parseDouble(AngleeditText.getText().toString());
double tnr = Double.parseDouble(TnreditText.getText().toString());

Any help is greatly appreciated. Thankk you in advance.

/** post to textView **/
XofftextView.setText(String.format("X Offset : %.4f", resultx));
ZofftextView.setText(String.format("Z Offset : %.4f", resultz));

Answer 1

Make sure you have checked null or empty before parsing to desired format.

Solution

String text = AngleeditText.getText().toString();

if (text != null && text.length() > 0) {
    double ang = Double.parseDouble(text);
    // Use ang value
}

Answer 2

Before processing input you should sanity check it.

Eg there's nothing wrong with doing something like:

String x = AngleeditText.getText().toString();
String y = TnreditText.getText().toString();

if (x == null || x.equalsIgnoreCase("") || y == null || y.equalsIgnoreCase("")) {
    return;
}

Just as a general rule the parsing should also always be wrapped in a try/catch control structure. Eg

double ang = 0.0;
double trn = 0.0;
try { 
    ang = Double.parseDouble(x);
    trn = Double.parseDouble(y);
} catch (Exception e) {
    //Optionally system.out or system.err some message here
    System.out.println("Couldn't parse" + x + " or " + y);
    return;
}

NB: you have to declare (and initialise) ang and trn if you want to use them outside of the try/catch block.

Additionally, even before trying to parse the input you might want to run it through an appropriate regex to make sure it's actually a legit number.

Answer 3

Biggkev. Welcome to programming world :)

Should I assume that resultx and resultz came from ang and tnr ? If so:

I believe when .ToString() function is called, AngleeditText.getText() returns no value. Since there is no reference, an exception blows afterwards, when you set resultx and resultz.

I suggest that you validate first if resultx and resultxz or AngleeditText.getText() and TnreditText.getText() return values different from null and empty.

You could create a method for that and include a validation like:

if(resultx != null && !resultx.isEmpty()) 
       XofftextView.setText(String.format("X Offset : %.4f", resultx));

I hope this is helpful.

Cheers