What if Textfield t1 is blank?? num1=Double.parseDouble(t1.getText());

Hi there
Im coding a simple calculator with 2 Textfield for entering two numbers. If one of Textfields is blank and an operation button (+,-,*,/) is clciked, I want the 3rd Textfield t3 to read "ERROR".
From the code below, what is num1 if t1 is blank. Or could you tell me how to go about this if statement.
if (ae.getSource()==multi){
               num1=Double.parseDouble(t1.getText());
               num2=Double.parseDouble(t2.getText());
               res=num1*num2;
               t3.setText(""+res);
cheers
SERGIO

I look forward to you figuring this out yourself.
1. What does getText() return when then JTextField is empty?
2. What happens when you pass that to parseDouble?
3. Should you even bother passing that to parseDouble?

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Sun must have been struggling for a bit 'cos it wasn't until JDK1.2 that they introduced Double.parseDouble, even though Integer.parseInt has been there since the dawn of time itself.
And since Microsoft stopped supported Java around JDK1.1.6 you'll probably find that your Applet is complaining that there's no such method (have a look in the Java Console in IE to see what it's got to say for itself).
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and read
http://docs.sun.com/source/806-3568/ncg_goldberg.html
This, too:http://java.sun.com/developer/JDCTechTips/2003/tt0204.html#2

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What if Textfield t1 is blank?? num1=Double.parseDouble(t1.getText());

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