CODEWITHSUNDEEP
java
zaib7777
zaib7777

Reputation: 89

To remove null values while traversing arraylist

I am trying with this code to replace null values in arraylist. I am getting null values in a tag in my xml file. Values in that tag are coming from arraylist. I want to remove null from tag and put nothing in place of it. My code is something like this:

    for(String s:a.getList){
here I setting values in tag by create tag and than appending child nodess using DOM parser.
}

where a=object that contains list

output is like this:

    <value>1</value>
<value>2</value>
<value>null</value>
<value>3</value>
<value>4</value>
<value>null</null>

. . .and so on

Expected output:

    <value>1</value>
<value>2</value>
<value/>
<value>3</value>
<value>4</value>
<value/>

null should be removed and tag should look something like this

code I am trying is:

  for(String s:a.list){
if(s.equals("null")){
s.replace("null","");
my code;

}

Always getting null pointer exception and don't know if this runs what will be output. Please help..

Upvotes: 0

Views: 806

Answers (3)

Arjun Nagathankandy
Arjun Nagathankandy

Reputation: 725

The best way to approach using array list is iterate from last to first if you want to remove concurrently.

for (int i = list.size()-1; i >= 0; i--) {
        if ("null".equalsIgnoreCase(list.get(i))) {
            list.remove(i);
        }
    }

"null".equalsIgnoreCase(list.get(i)) will avoid null pointer exception

For removing and printing value

for (String str  :  abc) {
        if ("null".equalsIgnoreCase(str)) {
            System.out.println("<value/>");
        } else {
            System.out.println("<value>"+str+"</value>");
        }
    }

Upvotes: 1

tomas
tomas

Reputation: 840

To make it clearer

public static void main(String... args) {
    ArrayList<String> a = new ArrayList<String>();
    a.add("one");
    a.add(null);
    a.add("two");
    a.removeAll(Collections.singleton(null));
    for(String value : a) {
        System.out.println(value);
    }
}

Output

one
two

Upvotes: 0

AxelH
AxelH

Reputation: 14572

You are not updating the list, you are creating a new String instance since String are immutable. Just set the value you want if the current value is "null"

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

The condition won't fail for null value, but if you want to replace those, you need to add the condition because for now, it will only update "null".

Upvotes: 1

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