如何比较java中if语句中的双值？

Question

I have a desktop application with textboxs that contain a price values. As an example if i input 25000

Double priceSec = Double.parseDouble(cusPrice.getText());

i'm passing that 25000 as a double value

so now i want to compare that value and check whether it is empty or not?

if(cusPrice2.getText()==null || cusPrice2.getText().isEmpty()){
        Double priceSec=0.0;
        }

i know i can create an else condition for

if textbox !=null
total=txtbox1+txtbox2+txtbox3;

if textbox value is empty or not empty. value should be there in total. but in my code ,it displays as null.

Do i have any other way to do that? can you tell me a way to do that.

here is my full code

  private void cusOkBtnActionPerformed(java.awt.event.ActionEvent evt) { 

    Double priceSec = Double.parseDouble(cusPrice2.getText());
    Double priceThird = Double.parseDouble(cusPrice3.getText());
    Double priceFourth = Double.parseDouble(cusPrice4.getText());
    Double priceFifth = Double.parseDouble(cusPrice5.getText());

    if(cusPrice2.getText()==null || cusPrice2.getText().isEmpty() || cusPrice2.getText() !=null ){
            priceSec=0.0;
            costCls.setItemPrice(priceSec);
            }
            else if(cusPrice3.getText()==null || cusPrice3.getText().isEmpty()){
            priceThird=0.0;
            }
            else if(cusPrice4.getText()==null || cusPrice4.getText().isEmpty()){
            priceFourth=0.0;
            }
            else if(cusPrice5.getText()==null || cusPrice5.getText().isEmpty()){
            priceFifth=0.0;
            }

           Double setItemTotal = priceCus+priceSec+priceThird+priceFourth+priceFifth;

}

Answer 1

You should rather use Exception s.

try {
    Double priceSec = Double.parseDouble(cusPrice.getText());
} catch (NullPointerException e1) {
    //null somewhere
} catch (NumberFormatException e2) {
    //not a number - on controlled input - empty field.
}

Answer 2

It is better to use the built-in Exception semantics already available within the Double.parseDouble(String s) implementation. (IMHO: Don't check up-front as you are making the exceptional-situation part of the normal flow)

Use a function like

private static double getValue(String str) {
    try {
        return  Double.parseDouble(str);
    } catch (NumberFormatException e) {
        return 0d;
    }
}

You would then use it like:

String priceStr = cusPrice.getText();
double d = getValue(priceStr);

Answer 3

double is the primitive type for floating point, Double is the Object child that wraps a double value. So:

double priceSec = Double.parseDouble(cusPrice.getText());

double price2Sec = cusPrice2.getText().isEmpty())
        ? 0.0
        : Double.parseDouble(cusPrice.getText());

if (priceSec == price2Sec) { ...

However for financial data a double has small approximation errors, that can become visible - especially with == . Hence one might better use BigDecimal, which does fixed point arithmetic.

 BigDecimal priceSec = new BigDecimal(cusPrice.getText());
 if (priceSec.compareTo(price2Sec) == 0) { ...

With a bit ugly API doing calculations:

 x = x.add(y.divide(new BigDecimal("12.50")));

Answer 4

you can try this

private void cusOkBtnActionPerformed(java.awt.event.ActionEvent evt) { 

    Double priceSec=0.0,priceThird=0.0,priceFourth=0.0,priceFifth=0.0;
    costCls.setItemPrice(0.0);


    if(cusPrice2.getText()!=null && !cusPrice2.getText().isEmpty() ){
        priceSec = Double.parseDouble(cusPrice2.getText());
        costCls.setItemPrice(priceSec);
    }
    else if(cusPrice3.getText()!=null && !cusPrice3.getText().isEmpty()){
        priceThird = Double.parseDouble(cusPrice3.getText());
    }
    else if(cusPrice4.getText()!=null && !cusPrice4.getText().isEmpty()){
        priceFourth = Double.parseDouble(cusPrice4.getText());
    }
    else if(cusPrice5.getText()!=null && !cusPrice5.getText().isEmpty()){
        priceFifth = Double.parseDouble(cusPrice5.getText());
    }

   Double setItemTotal = priceCus+priceSec+priceThird+priceFourth+priceFifth;

}