Every time i append a string in for loop , i get a null in between

Question

So I am running a string append statement inside a for loop

String apComment;
apComment = ''; 
for(Processinstancehistory p:lispros)
{
    apComment +=p.Comments;
}

So after this, I get the comments in below way

Comment1nullComment2Comment3

I get a null in between. Can someone please help how to remove this null

Answer 1

+Dan's response..

You can use null check before appending it to your string..

String apComment = ''; 
for(Processinstancehistory p:lispros)
{
    if (string.isNotBlank(p.Comments)) {
        apComment +=p.Comments;
    }
}

or you can create a list of comments and use string.join as suggested..

String apComment = '';
List<String> comments = new List<String>();
for(Processinstancehistory p:lispros)
{
    if (string.isNotBlank(p.Comments)) {
        comments.add(p.Comments);
    }
}

if (!comments.isEmpty()) {
    apComment = string.join(comments, ',');
}

Answer 2

I'd recommend using String.join() instead of trying to handle the concatenation yourself. This really goes for anything where Salesforce provides us with standard logic they've built themselves. It saves us time, is probably better-written, and is almost certainly better-optimized.