Question

I’ve been reading up on the net about the issues with handling float and double types in java. Unfortunately, the image is still not clear. Hence, i’m asking here direct. 🙁

My MySQL table has various DECIMAL(m,d) columns. The m may range from 5 to 30. d stays a constant at 2.

Question 1.

What equivalent data-type should i be using in Java to work (i.e store, retrieve, and process) with the size of the values in my table? (I’ve settled with double – hence this post).

Question 2.

While trying to parse a double from a string, i’m getting errors

Double dpu = new Double(dpuField.getText());

for example –

"1" -> java.lang.NumberFormatException: empty String
"10" -> 1.0
"101" -> 10.0
"101." -> 101.0
"101.1" -> 101.0
"101.19" -> 101.1

What am i doing wrong? What is the correct way to convert a string to a double value?
And what measures should i take to perform operations on such values?

EDIT

This is the code –

    System.out.println(dpuField.getText());
    Double dpu = new Double(dpuField.getText());
    System.out.println(dpu);

Yes, the problem lies with getText() reporting the wrong value of the dpuField.
This method is called on the JTextField keyTyped event. So what’s going wrong here?

EDIT 2

Looking at :
http://journals.ecs.soton.ac.uk/java/tutorial/post1.0/ui/keylistener.html
Apparently, keyTyped() does not give me the keycode. I’ll have to switch to keyRealeased()

Answer 1

What equivalent data-type should i be using in Java to work (i.e store, retrieve, and process) with the size of the values in my table? (I’ve settled with double – hence this post).

Since it’s a DECIMAL field, you should prefer java.math.BigDecimal. You can store it in DB using PreparedStatement#setBigDecimal() and you can retrieve it from DB using ResultSet#getBigDecimal().

While trying to parse a double from a string, i’m getting errors

This can’t be true. The problem lies somewhere else. Maybe it is just not returning the data you expect to be returned or you are not using/debugging the values you expect them to be.