import java.util.ArrayList;
import java.util.List;
public class Example {
public static void main(String[] args) {
List<String> stringList = new ArrayList<>();
stringList.add("Java");
stringList.add("Example");
stringList.add("Text");
stringList.add(null);
stringList.forEach(str -> System.out.println(str.substring(1))); //error
}
}
In the above example as you can see I am iterating through a ArrayList of Strings that have a null value as well, so when I use forEach loop over it and iterate and do a subString on the array elements, I will get an NPE (Null Pointer Exception)
Output:Exception in thread "main" java.lang.NullPointerException: Cannot invoke "String.substring(int)" because "str" is null
at Example.lambda$main$0(Example.java:14)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at Example.main(Example.java:14)
So as a developer you would need to handle the Unchecked NPE!
import java.util.ArrayList;
import java.util.List;
public class Example {
public static void main(String[] args) {
List<String> stringList = new ArrayList<>();
stringList.add("Java");
stringList.add("Example");
stringList.add("Text");
stringList.add(null);
stringList.forEach(str -> {
if(str == null) {
System.out.println("NULL Value");
} else {
System.out.println(str.substring(1));
}
});
}
}

Java 8 Exception - cannot invoke because the object is null
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