Replace Null Values in Arraylist

Question

i'm trying to replace null values in my arrayList but I get exception

java.lang.NullPointerException

I have tried different way :

Data.replaceAll(s -> s.replaceAll(" null", ""));

And :

for(int x = 0; x < Data.size(); x++)
          {
                if(Data.get(x).equals("null") == true)
                {
                    Data.set(x, "");
                }
          }

And :

for(int x = 0; x < Data.size(); x++)
          {
                if(Data.get(x).equals(null) == true)
                {
                    Data.set(x, "");
                }
          }

but an exception is throw java.lang.NullPointerException

Here is an exemple of my arrayList:

[0050568D6268, null, A001, A, T3, Principal, COL - Test, 4-Lock, Com. On Stage, Social, RDC, null, null, null, null, -1, null, -1, 0, -1, 99, 53]

I'm looking for any help thanks.

Note that when asking about exceptions you should post the entire stacktrace and mark the mentioned lines in the code you've posted. — Thomas
– Thomas, Commented Oct 14, 2019 at 9:14
I'm using Talend so the stacktrace is like this : Exception in component tJava_3 (LOTS_ACTIF_CREMAJ) java.lang.NullPointerException at genio.lots_actif_cremaj_0_1.LOTS_ACTIF_CREMAJ.lambda$0(LOTS_ACTIF_CREMAJ.java:2158) at java.util.ArrayList.replaceAll(Unknown Source) at genio.lots_actif_cremaj_0_1.LOTS_ACTIF_CREMAJ.tJava_3Process(LOTS_ACTIF_CREMAJ.java:2158) at genio.lots_actif_cremaj_0_1.LOTS_ACTIF_CREMAJ.tDBInput_6Process(LOTS_ACTIF_CREMAJ.java:1969) — PandaRasta
– PandaRasta, Commented Oct 14, 2019 at 9:15
Why do you think Data.get(x).equals(null) would not throw an exception when that entry is nul? Since when can someone call a method like .equals on a null object? — Tom
– Tom, Commented Oct 14, 2019 at 9:16

Tim Biegeleisen · Accepted Answer · 2019-10-14 09:15:41Z

5

I think you want to use map() here:

// given list data
data = data.stream()
    .map(s -> Objects.isNull(s) ? "" : s)
    .collect(Collectors.toList());

This would return a list identical to the input, except with all null values replaced by empty string.

answered Oct 14, 2019 at 9:15

Tim Biegeleisen

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3 Comments

JonK Over a year ago

You could also use .filter(Objects::nonNull) to just exclude the null elements if you don't need to replace them with some default

Tim Biegeleisen Over a year ago

@JonK Yes, but my understanding of the OP is that he wants to replace and retain the originally null values.

PandaRasta Over a year ago

@Tim Biegeleisen Exactly

rdas · Accepted Answer · 2019-10-14 09:23:27Z

5

The values in your list seem to be actual nulls and not strings with "null". You can replace these with "" by:

data.replaceAll(t -> Objects.isNull(t) ? "" : t);

You can remove them with:

data.removeIf(Objects::isNull)

edited Oct 14, 2019 at 9:23

answered Oct 14, 2019 at 9:14

rdas

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2 Comments

PandaRasta Over a year ago

I don't want to remove it I want to replace it with empty string.

rdas Over a year ago

@PandaRasta Added to the answer

Gustavo Pagani · Accepted Answer · 2019-10-14 09:14:00Z

2

in this line you are comparing the value at position x with the String null and not "with a null value":

if(Data.get(x).equals("null") == true)

Replace this comparison by:

if(Data.get(x) == null)

answered Oct 14, 2019 at 9:14

Gustavo Pagani

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4 Comments

PandaRasta Over a year ago

Worked perfectly! I accept the solution. An idea why Data.replaceAll(s -> s.replaceAll(null, ""));throws an exception ? Because I use it exactly like this on an other program and it worked.

Gustavo Pagani Over a year ago

it's throwing an exception because you are trying to call replaceAll on a null object when you call s.replaceAll

Gustavo Pagani Over a year ago

you should do what @rdas suggested in his answer: Data.replaceAll(s -> Objects.isNull(s) ? "" : s);

PandaRasta Over a year ago

Yes but what I don't get is it's working on an other arraylist with mixing null values and string values.

Tom · Accepted Answer · 2019-12-03 11:23:28Z

2

We can not call any method on a null object, that is the reason why you get a NullPointerException.

Below line is throwing NullPointerException because calling equals method on null object is not allowed in Java.

Data.get(x).equals("null")

So replacing above with below will solve the issue.

Data.get(x) == null

Also, there is no need for the extra comparison with == true.

edited Dec 3, 2019 at 11:23

Tom

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answered Oct 14, 2019 at 9:34

Krutik Jayswal

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