I have an List array 'details'.
List<HistoryDetails> details
where HistoryDetails is an object containing strings.
When I check the size it gives me a positive value.
details.size()
But when I try to access an element it throws a null pointer exception.
details.get(0).getFirstElement();
Attempt to invoke virtual method 'java.lang.String com.HistoryDetails.getFirstElement()' on a null object reference
I am invoking the element at the very next line to where I check the size. Hence, nothing should be reset. What could be wrong?
It looks like details
is a List
, but the first element of the List
is null. That is, it looks like details.get(0) == null
.
A List details
having many items can have first item a null object. before using that item check null.
if(details.get(0)!=null){
details.get(0).getFirstElement();
}
因为它包含null。
Log.d("TEST", details.get(0)); //should return null
This will avoid the null pointer exception:
if (!details.isEmpty()) {
details.get(0).getFirstElement();
}
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