topic Simple case with a column which contains Double : I dont understand this error with java.lang.NullPointerException in Talend Studio

Simple case with a column which contains Double : I dont understand this error with java.lang.NullPointerException

citrods — Tue, 20 Apr 2021 08:21:29 GMT

Hello

I have a very simple transformation with a tMap which deals with a column with has Double.

My input file is simple :

In my output file, I want to fill in the 2 column with 1.5 if the type of room is related to "group A"

I use a tMap :

My tMap is set as such:

When i run the job , I have a message error with java.lang.NullPointerException.

however, if my second column "area" is set a String instead of a double and in the tmap I write

row1.group.equals("Group A")? "1.5": row1.area

Then it works perfectly.

However I need a double as I will later perform some mathematical operations later.

can you explain why i doesn't work with a double?

Re: Simple case with a column which contains Double : I dont understand this error with java.lang.NullPointerException

gjeremy1617088143 — Tue, 20 Apr 2021 12:33:53 GMT

HI, I reproduce your error , it's because row1.area can be null when group not equals Group A and ternary in the Tmap seems to don't work with nullable Double( this is weird cause Double like Integer support nullable values) . To bypass this I make a custom routine :

package routines;

public class Double_routine {

public static Double check(String group,Double area ) {

if ("Group A".equals(group)) {

return 1.5;

}

return area;

}

and in the Tmap I call it : Double_routine.check(row1.group,row1.area)

and it's work !

Send me Love and Kudos

Re: Simple case with a column which contains Double : I dont understand this error with java.lang.NullPointerException

gjeremy1617088143 — Tue, 20 Apr 2021 13:51:35 GMT

after few search you could use this : "Group A".equals(row1.group)? new Double(1.5): row1.area.

If any of the operands is of a reference type, unboxing conversion is performed. Then: If either operand is of type double, the other is converted to double instead of Double

Re: Simple case with a column which contains Double : I dont understand this error with java.lang.NullPointerException

citrods — Wed, 21 Apr 2021 15:19:36 GMT

hello

i'm a beginner. What do you mean by custom routine and package routines?

can I have a screenshot of the job you made?

Also i dudn't get your 2nd message

"if any of the operands is of a reference type, unboxing conversion is performed. Then: If either operand is of type double, the other is converted to double instead of Double"

what is an unboxing conversion?

what is the difference between double and Double?

Re: Simple case with a column which contains Double : I dont understand this error with java.lang.NullPointerException

gjeremy1617088143 — Wed, 21 Apr 2021 21:12:33 GMT

Hi, double is a primitive java type and Double is a wrapper of double, so double is not nullable, Double is nullable.when you write 1.5 in your ternary it read it as a double and so it read row1.area as a double( it’ a consequence of the ternary autoboxing) , some values of area are null then it throw a null pointer exception. To avoid this you have to write new Double(1.5) then row1.area will be interpreted as a Double in the ternary expression and output will accept null value. An other way to avoid that is to write a simple routine with Double as return Value( the full code of the routine is in the first sentence). A routine in talend is similar to a java class. You can find them on the repository view —> Code—> Routines. You can write your own by the way. Send me Love and Kudos

Re: Simple case with a column which contains Double : I dont understand this error with java.lang.NullPointerException

gjeremy1617088143 — Fri, 07 May 2021 07:24:02 GMT

Hi, if my answer is ok , could you select it as the best please

Re: Simple case with a column which contains Double : I dont understand this error with java.lang.NullPointerException

citrods — Fri, 07 May 2021 14:12:35 GMT