Java8 Lists return element or null

user_4450024 0
Viewed 198

I have this piece of code, where I want to return an element if present, otherwise null

List<String> myList = new ArrayList<>();
myList.add("Test");
myList.add("Example");
myList.add("Sth");

String str = myList.stream()
            .filter(x -> x.equals("eee"))
            .findFirst()
            .orElseGet(null);

but I got an Exception in thread "main" java.lang.NullPointerException anyway

java-stream java-8 option-type functional-programming java
2 Answers

orElseGet takes a supplier. You want to use orElse:

.findFirst().orElse(null);

It doesn't make much sense to use a supplier to return null, but if you were to, it would look like:

.findFirst().orElseGet(() -> null); //if argument is null, you get the NPE

The JavaDocs of orElseGet (thanks to bambam's comment for the addition) mention it:

Throws:
NullPointerException - if value is not present and other is null

user_57615580

Try this code:

List<String> myList = new ArrayList<>();
myList.add("Test");
myList.add("Example");
myList.add("Sth");

String str = myList.stream()
        .filter(s -> null != s && s.equals("Test"))
        .findFirst()
        .orElseGet(() -> null);
System.out.println(str);
user_63759170
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