Question

I am trying to call a custom catch expression

String value1 = side1_tb.getText();
String value2 = side2_tb.getText();
String value3 = side3_tb.getText();
try
{
    result_lbl.setText(
        actual_triangle.Triangle(
            Double.parseDouble(value1),
            Double.parseDouble(value2),
            Double.parseDouble(value3)));
}
catch (NumberFormatException exe)
{

}

So from the above code you can see that there are three textboxes values are being assigned to a string variables and then I implemented a try and catch method with ‘Numberformatexception’ but in the place of ‘Numberformatexception’ I want to implement a custom exception and this exception will be declared in another class lets call this class EXCEPTIONclass.java and in here I want to create an exception if String values are not being able to parse to double values, which I am trying to achieve in the above code.

Not really sure how to extend the exception class and then declare a new exception.

Answer 1

You could do it as follows:

public class MyCustomException extends Exception
{
    // To keep compiler happy about Exception being serializable.
    // Note: This should carry meaningful value when these exceptions are going 
    // to be serialized
    public static final long serialVersionUID = 1L; 

    public MyCustomException(String message, Throwable t)
    {
        super(message, t);
    }

    // Other constructors of interest from the super classes.
}

In your catch block, you would wrap the NumberFormatException as follows:

catch (NumberFormatException nfe)
{
    throw new MyCustomException("<Your message>", nfe);
}