Question

I wrote the following code to take input from user and parse it to double for further calculations. The problem is this program is giving me java.lang.NumberFormatException at compile time and this error java.lang.Double.parseDouble(Unknown Source). I don’t know why is this error is generated. So my questions are:

• What is the cause of this error?
• Why am I getting exception at compile time. In C++ if something went wrong, I would get exception at run time. I am unable to understand this behavior of Java.

Here is the code:

Note:

Multiplicand and Multiplier are JTextField

public void TakeInput()
{
     double a,b;
    String input1="1",input2="1";

    input1=Multiplicand.getText();
    input2=Multiplier.getText();

    a=Double.parseDouble(input1);// converting string input to double
    b=Double.parseDouble(input2);
   ....
}

When I click run or play button in eclipse, I get this exception. So thats why I am unable to give any input to these text fields

Regards

Answer 1

When I click run or play button in eclipse, I get this exception.

Your initial values for Multiplicand and Multiplier must be valid double values for Double.parseDouble not to throw a NumberFormatException.

Note that if you wish to set the values in each JTextField to 1 you could do:

Multiplicand.setText("1");
Multiplier.setText("1");

Also, NumberFormatException is a runtime or unchecked exception. You could wrap your assignments in a try/catch block so that you can handle this exception gracefully.